Oracle® Database SQL Reference 10g Release 1 (10.1) Part Number B10759-01 |
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Each value manipulated by Oracle Database has a datatype. The datatype of a value associates a fixed set of properties with the value. These properties cause Oracle to treat values of one datatype differently from values of another. For example, you can add values of NUMBER
datatype, but not values of RAW
datatype.
When you create a table or cluster, you must specify a datatype for each of its columns. When you create a procedure or stored function, you must specify a datatype for each of its arguments. These datatypes define the domain of values that each column can contain or each argument can have. For example, DATE
columns cannot accept the value February 29 (except for a leap year) or the values 2 or 'SHOE'. Each value subsequently placed in a column assumes the datatype of the column. For example, if you insert '01-JAN-98'
into a DATE
column, then Oracle treats the '01-JAN-98'
character string as a DATE
value after verifying that it translates to a valid date.
Oracle Database provides a number of built-in datatypes as well as several categories for user-defined types that can be used as datatypes. The syntax of Oracle datatypes appears in the diagrams that follow. The text of this section is divided into the following sections:
The Oracle precompilers recognize other datatypes in embedded SQL programs. These datatypes are called external datatypes and are associated with host variables. Do not confuse built-in datatypes and user-defined types with external datatypes. For information on external datatypes, including how Oracle converts between them and built-in datatypes or user-defined types, see Pro*COBOL Programmer's Guide, and Pro*C/C++ Programmer's Guide.
For descriptions of the Oracle built-in datatypes, please refer to "Oracle Built-in Datatypes".
The ANSI-supported datatypes appear in the figure that follows. "ANSI, DB2, and SQL/DS Datatypes " discusses the mapping of ANSI-supported datatypes to Oracle built-in datatypes.
For a description of the expression_filter_type
, please refer to "Expression Filter Type". Other Oracle-supplied types follow:
For descriptions of the Any
types, please refer to "Any Types ".
For descriptions of the XML types, please refer to "XML Types ".
For descriptions of the spatial types, please refer to "Spatial Types ".
For descriptions of the media types, please refer to "Media Types ".
The table that follows summarizes Oracle built-in datatypes. The codes listed for the datatypes are used internally by Oracle Database. The datatype code of a column or object attribute is returned by the DUMP function.
Table 2-1 Built-In Datatype Summary
Code | Built_in Datatype | Description |
---|---|---|
1 | VARCHAR2( size [BYTE | CHAR]) |
Variable-length character string having maximum length size bytes or characters. Maximum size is 4000 bytes or characters, and minimum is 1 byte or 1 character. You must specify size for VARCHAR2 .
|
1 | NVARCHAR2( size) |
Variable-length character string having maximum length size characters. Maximum size is determined by the national character set definition, with an upper limit of 4000 bytes. You must specify size for NVARCHAR2 . |
2 | NUMBER( p,s ) |
Number having precision p and scale s . The precision p can range from 1 to 38. The scale s can range from -84 to 127. |
8 | LONG |
Character data of variable length up to 2 gigabytes, or 231 -1 bytes. |
12 | DATE |
Valid date range from January 1, 4712 BC to December 31, 9999 AD. |
21 | BINARY_FLOAT |
32-bit floating point number. This datatype requires 5 bytes, including the length byte. |
22 | BINARY_DOUBLE |
64-bit floating point number. This datatype requires 9 bytes, including the length byte. |
180 | TIMESTAMP (fractional_seconds_precision ) |
Year, month, and day values of date, as well as hour, minute, and second values of time, where fractional_seconds_precision is the number of digits in the fractional part of the SECOND datetime field. Accepted values of fractional_seconds_precision are 0 to 9. The default is 6. |
181 | TIMESTAMP (fractional_seconds_precision ) WITH TIME ZONE |
All values of TIMESTAMP as well as time zone displacement value, where fractional_seconds_precision is the number of digits in the fractional part of the SECOND datetime field. Accepted values are 0 to 9. The default is 6. |
231 | TIMESTAMP (fractional_seconds_precision ) WITH LOCAL TIME ZONE |
All values of TIMESTAMP WITH TIME ZONE , with the following exceptions:
|
182 | INTERVAL YEAR (year_precision ) TO MONTH |
Stores a period of time in years and months, where year_precision is the number of digits in the YEAR datetime field. Accepted values are 0 to 9. The default is 2. |
183 | INTERVAL DAY (day_precision ) TO SECOND (fractional_seconds_precision ) |
Stores a period of time in days, hours, minutes, and seconds, where
|
23 | RAW( size ) |
Raw binary data of length size bytes. Maximum size is 2000 bytes. You must specify size for a RAW value. |
24 | LONG RAW |
Raw binary data of variable length up to 2 gigabytes. |
69 | ROWID |
Base 64 string representing the unique address of a row in its table. This datatype is primarily for values returned by the ROWID pseudocolumn. |
208 | UROWID [( size )] |
Base 64 string representing the logical address of a row of an index-organized table. The optional size is the size of a column of type UROWID . The maximum size and default is 4000 bytes. |
96 | CHAR( size [BYTE | CHAR]) |
Fixed-length character data of length size bytes. Maximum size is 2000 bytes or characters. Default and minimum size is 1 byte.
|
96 | NCHAR( size ) |
Fixed-length character data of length size characters. Maximum size is determined by the national character set definition, with an upper limit of 2000 bytes. Default and minimum size is 1 character. |
112 | CLOB |
A character large object containing single-byte or multibyte characters. Both fixed-width and variable-width character sets are supported, both using the database character set. Maximum size is (4 gigabytes - 1) * (database block size). |
112 | NCLOB |
A character large object containing Unicode characters. Both fixed-width and variable-width character sets are supported, both using the database national character set. Maximum size is (4 gigabytes - 1) * (database block size). Stores national character set data. |
113 | BLOB |
A binary large object. Maximum size is (4 gigabytes - 1) * (database block size). |
114 | BFILE |
Contains a locator to a large binary file stored outside the database. Enables byte stream I/O access to external LOBs residing on the database server. Maximum size is 4 gigabytes. |
Character datatypes store character (alphanumeric) data, which are words and free-form text, in the database character set or national character set. They are less restrictive than other datatypes and consequently have fewer properties. For example, character columns can store all alphanumeric values, but NUMBER
columns can store only numeric values.
Character data is stored in strings with byte values corresponding to one of the character sets, such as 7-bit ASCII or EBCDIC, specified when the database was created. Oracle Database supports both single-byte and multibyte character sets.
These datatypes are used for character data:
The CHAR
datatype specifies a fixed-length character string. Oracle ensures that all values stored in a CHAR
column have the length specified by size
. If you insert a value that is shorter than the column length, then Oracle blank-pads the value to column length. If you try to insert a value that is too long for the column, then Oracle returns an error.
The default length for a CHAR
column is 1 byte and the maximum allowed is 2000 bytes. A 1-byte string can be inserted into a CHAR(10)
column, but the string is blank-padded to 10 bytes before it is stored.
When you create a table with a CHAR
column, by default you supply the column length in bytes. The BYTE
qualifier is the same as the default. If you use the CHAR
qualifier, for example CHAR
(10
CHAR
), then you supply the column length in characters. A character is technically a code point of the database character set. Its size can range from 1 byte to 4 bytes, depending on the database character set. The BYTE
and CHAR
qualifiers override the semantics specified by the NLS_LENGTH_SEMANTICS
parameter, which has a default of byte semantics. For performance reasons, Oracle recommends that you use the NLS_LENGTH_SEMANTICS
parameter to set length semantics and that you use the BYTE
and CHAR
qualifiers only when necessary to override the parameter.
To ensure proper data conversion between databases with different character sets, you must ensure that CHAR
data consists of well-formed strings. See Oracle Database Globalization Support Guide for more information on character set support.
The NCHAR
datatype is a Unicode-only datatype. When you create a table with an NCHAR
column, you define the column length in characters. You define the national character set when you create your database.
The maximum length of a column is determined by the national character set definition. Width specifications of character datatype NCHAR
refer to the number of characters. The maximum column size allowed is 2000 bytes.
If you insert a value that is shorter than the column length, then Oracle blank-pads the value to column length. You cannot insert a CHAR
value into an NCHAR
column, nor can you insert an NCHAR
value into a CHAR
column.
The following example compares the translated_description
column of the pm.product_descriptions
table with a national character set string:
SELECT translated_description FROM product_descriptions WHERE translated_name = N'LCD Monitor 11/PM';
Please refer to Oracle Database Globalization Support Guide for information on Unicode datatype support.
The NVARCHAR2
datatype is a Unicode-only datatype. When you create a table with an NVARCHAR2
column, you supply the maximum number of characters it can hold. Oracle subsequently stores each value in the column exactly as you specify it, provided the value does not exceed the maximum length of the column.
The maximum length of the column is determined by the national character set definition. Width specifications of character datatype NVARCHAR2
refer to the number of characters. The maximum column size allowed is 4000 bytes. Please refer to Oracle Database Globalization Support Guide for information on Unicode datatype support.
The VARCHAR2
datatype specifies a variable-length character string. When you create a VARCHAR2
column, you supply the maximum number of bytes or characters of data that it can hold. Oracle subsequently stores each value in the column exactly as you specify it, provided the value does not exceed the column's maximum length of the column. If you try to insert a value that exceeds the specified length, then Oracle returns an error.
You must specify a maximum length for a VARCHAR2
column. This maximum must be at least 1 byte, although the actual string stored is permitted to be a zero-length string (''
). You can use the CHAR
qualifier, for example VARCHAR2
(10
CHAR
), to give the maximum length in characters instead of bytes. A character is technically a code point of the database character set. CHAR
and BYTE
qualifiers override the setting of the NLS_LENGTH_SEMANTICS
parameter, which has a default of bytes. For performance reasons, Oracle recommends that you use the NLS_LENGTH_SEMANTICS
parameter to set length semantics and that you use the BYTE
and CHAR
qualifiers only when necessary to override the parameter. The maximum length of VARCHAR2
data is 4000 bytes. Oracle compares VARCHAR2
values using nonpadded comparison semantics.
To ensure proper data conversion between databases with different character sets, you must ensure that VARCHAR2
data consists of well-formed strings. See Oracle Database Globalization Support Guide for more information on character set support.
The VARCHAR
datatype is currently synonymous with the VARCHAR2
datatype. Oracle recommends that you use VARCHAR2
rather than VARCHAR
. In future releases, VARCHAR
might be defined as a separate datatype used for variable-length character strings compared with different comparison semantics.
The Oracle Database numeric datatypes store positive and negative fixed and floating-point numbers, zero, infinity, and values that are the undefined result of an operation (that is, is "not a number" or NAN
).
The NUMBER
datatype stores zero as well as positive and negative fixed numbers with absolute values from 1.0 x 10-130 to (but not including) 1.0 x 10126. If you specify an arithmetic expression whose value has an absolute value greater than or equal to 1.0 x 10126, then Oracle returns an error. Each NUMBER
value requires from 1 to 22 bytes.
Specify a fixed-point number using the following form:
NUMBER(p,s)
where:
p
is the precision, or the total number of digits. Oracle guarantees the portability of numbers with precision of up to 38 digits.
s
is the scale, or the number of digits to the right of the decimal point. The scale can range from -84 to 127.
Specify an integer using the following form:
NUMBER(p)
This represents a fixed-point number with precision p
and scale 0 and is equivalent to NUMBER(p,0)
.
Specify a floating-point number using the following form:
NUMBER
The absence of precision and scale designators specifies the maximum range and precision for an Oracle number.
Specify the scale and precision of a fixed-point number column for extra integrity checking on input. Specifying scale and precision does not force all values to a fixed length. If a value exceeds the precision, then Oracle returns an error. If a value exceeds the scale, then Oracle rounds it.
Table 2-2 show how Oracle stores data using different precisions and scales.
Table 2-2 Storage of Scale and Precision
Actual Data | Specified As | Stored As |
---|---|---|
7456123.89 | NUMBER |
7456123.89 |
7456123.89 | NUMBER(9) |
7456124 |
7456123.89 | NUMBER(9,2) |
7456123.89 |
7456123.89 | NUMBER(9,1) |
7456123.9 |
7456123.89 | NUMBER(6) |
exceeds precision |
7456123.89 | NUMBER(7,-2) |
7456100 |
7456123.89 | NUMBER(7,2) |
exceeds precision |
If the scale is negative, then the actual data is rounded to the specified number of places to the left of the decimal point. For example, a specification of (10,-2) means to round to hundreds.
You can specify a scale that is greater than precision, although it is uncommon. In this case, the precision specifies the maximum number of digits to the right of the decimal point. As with all number datatypes, if the value exceeds the precision, then Oracle returns an error message. If the value exceeds the scale, then Oracle rounds the value. For example, a column defined as NUMBER(4,5)
requires a zero for the first digit after the decimal point and rounds all values past the fifth digit after the decimal point. Table 2-3 show the effects of a scale greater than precision:
Floating-point numbers can have a decimal point anywhere from the first to the last digit or can have no decimal point at all. An exponent may optionally be used following the number to increase the range (for example, 1.777 e-20). A scale value is not applicable to floating-point numbers, because the number of digits that can appear after the decimal point is not restricted.
Binary floating-point numbers differ from NUMBER
in the way the values are stored internally by Oracle Database. Values are stored using decimal precision for NUMBER
. All literals that are within the range and precision supported by NUMBER
are stored exactly as NUMBER
. Literals are stored exactly because literals are expressed using decimal precision (the digits 0 through 9). Binary floating-point numbers are stored using binary precision (the digits 0 and 1). Such a storage scheme cannot represent all values using decimal precision exactly. Frequently, the error that occurs when converting a value from decimal to binary precision is undone when the value is converted back from binary to decimal precision. The literal 0.1 is such an example.
Oracle Database provides two numeric datatypes exclusively for floating-point numbers:
BINARY_FLOAT
is a 32-bit, single-precision floating-point number datatype. Each BINARY_FLOAT
value requires 5 bytes, including a length byte.
BINARY_DOUBLE
is a 64-bit, double-precision floating-point number datatype. Each BINARY_DOUBLE
value requires 9 bytes, including a length byte.
In a NUMBER
column, floating point numbers have decimal precision. In a BINARY_FLOAT
or BINARY_DOUBLE
column, floating-point numbers have binary precision. The binary floating-point numbers support the special values infinity and NaN
(not a number).
You can specify floating-point numbers within the limits listed in Table 2-4. The format for specifying floating-point numbers is defined in "Numeric Literals ".
Table 2-4 Floating Point Number Limits
Value | Binary-Float | Binary-Double |
---|---|---|
Maximum finite value | 1.79e308 | 3.4e38 |
Minimum finite value | -1.79e308 | -3.4e38 |
Smallest positive value | 2.3e-308 | 1.2e-38 |
Smallest negative value | -2.3e-308 | -1.2e-38 |
Oracle Database also supports the ANSI datatype FLOAT
. You can specify this datatype using one of these syntactic forms:
FLOAT FLOAT(n)
The number n
indicates the number of bits of precision that the value can store. The value for n
can range from 1 to 126. To convert from binary to decimal precision, multiply n
by 0.30103. To convert from decimal to binary precision, multiply the decimal precision by 3.32193. The maximum of 126 digits of binary precision is roughly equivalent to 38 digits of decimal precision.
The Oracle implementation of floating-point datatypes conforms substantially with the Institute of Electrical and Electronics Engineers (IEEE) Standard for Binary Floating-Point Arithmetic, IEEE Standard 754-1985 (IEEE754). The new datatypes conform to IEEE754 in the following areas:
The SQL function SQRT
implements square root. See SQRT .
The SQL function REMAINDER
implements remainder. See REMAINDER .
Arithmetic operators conform. See "Arithmetic Operators ".
Comparison operators conform, except for comparisons with NaN
. Oracle orders NaN
greatest with respect to all other values, and evaluates NaN
equal to NaN
. See "Floating-Point Conditions ".
Conversion operators conform. See "Conversion Functions ".
The default rounding mode is supported.
The default exception handling mode is supported.
The special values INF
, -INF
, and NaN
are supported. See "Floating-Point Conditions ".
Rounding of BINARY_FLOAT
and BINARY_DOUBLE
values to integer-valued BINARY_FLOAT
and BINARY_DOUBLE
values is provided by the SQL functions ROUND
, TRUNC
, CEIL
, and FLOOR
.
Rounding of BINARY_FLOAT
/BINARY_DOUBLE
to decimal and decimal to BINARY_FLOAT
/BINARY_DOUBLE
is provided by the SQL functions TO_CHAR
, TO_NUMBER
, TO_NCHAR
, TO_BINARY_FLOAT
, TO_BINARY_DOUBLE
, and CAST
.
The new datatypes do not conform to IEEE754 in the following areas:
-0 is coerced to +0.
Comparison with NaN
is not supported.
All NaN
values are coerced to either BINARY_FLOAT_NAN
or BINARY_DOUBLE_NAN
.
Non-default rounding modes are not supported.
Non-default exception handling mode are not supported.
Numeric precedence determines, for operations that support numeric datatypes, the datatype Oracle uses if the arguments to the operation have different datatypes. BINARY_DOUBLE
has the highest numeric precedence, followed by BINARY_FLOAT
, and finally by NUMBER
. Therefore, in any operation on multiple numeric values:
If any of the operands is BINARY_DOUBLE
, then Oracle attempts to convert all the operands implicitly to BINARY_DOUBLE
before performing the operation.
If none of the operands is BINARY_DOUBLE
but any of the operands is BINARY_FLOAT
, then Oracle attempts to convert all the operands implicitly to BINARY_FLOAT
before performing the operation.
Otherwise, Oracle attempts to convert all the operands to NUMBER
before performing the operation.
If any implicit conversion is needed and fails, then the operation fails. Table 2-11, "Implicit Type Conversion Matrix" for more information on implicit conversion.
In the context of other datatypes, numeric datatypes have lower precedence than the datetime/interval datatypes and higher precedence than character and all other datatypes.
LONG
columns store variable-length character strings containing up to 2 gigabytes -1, or 231-1 bytes. LONG
columns have many of the characteristics of VARCHAR2
columns. You can use LONG
columns to store long text strings. The length of LONG
values may be limited by the memory available on your computer.
Do not create tables with LONG
columns. Use LOB columns (CLOB
, NCLOB
, BLOB
) instead. LONG
columns are supported only for backward compatibility.
Oracle also recommends that you convert existing LONG
columns to LOB columns. LOB columns are subject to far fewer restrictions than LONG
columns. Further, LOB functionality is enhanced in every release, whereas LONG
functionality has been static for several releases. See the modify_col_properties
clause of ALTER TABLE and TO_LOB for more information on converting LONG
columns to LOB.
You can reference LONG
columns in SQL statements in these places:
SELECT
lists
SET
clauses of UPDATE
statements
VALUES
clauses of INSERT
statements
The use of LONG
values is subject to these restrictions:
A table can contain only one LONG
column.
You cannot create an object type with a LONG
attribute.
LONG
columns cannot appear in WHERE
clauses or in integrity constraints (except that they can appear in NULL
and NOT
NULL
constraints).
LONG
columns cannot be indexed.
LONG
data cannot be specified in regular expressions.
A stored function cannot return a LONG
value.
You can declare a variable or argument of a PL/SQL program unit using the LONG
datatype. However, you cannot then call the program unit from SQL.
Within a single SQL statement, all LONG
columns, updated tables, and locked tables must be located on the same database.
LONG
and LONG
RAW
columns cannot be used in distributed SQL statements and cannot be replicated.
If a table has both LONG
and LOB columns, then you cannot bind more than 4000 bytes of data to both the LONG
and LOB columns in the same SQL statement. However, you can bind more than 4000 bytes of data to either the LONG
or the LOB column.
In addition, LONG
columns cannot appear in these parts of SQL statements:
GROUP
BY
clauses, ORDER
BY
clauses, or CONNECT
BY
clauses or with the DISTINCT
operator in SELECT
statements
The UNIQUE
operator of a SELECT
statement
The column list of a CREATE
CLUSTER
statement
The CLUSTER
clause of a CREATE
MATERIALIZED
VIEW
statement
SQL built-in functions, expressions, or conditions
SELECT
lists of queries containing GROUP
BY
clauses
SELECT
lists of subqueries or queries combined by the UNION
, INTERSECT
, or MINUS
set operators
SELECT
lists of CREATE
TABLE
... AS
SELECT
statements
ALTER
TABLE
... MOVE
statements
SELECT
lists in subqueries in INSERT
statements
Triggers can use the LONG
datatype in the following manner:
A SQL statement within a trigger can insert data into a LONG
column.
If data from a LONG
column can be converted to a constrained datatype (such as CHAR
and VARCHAR2
), then a LONG
column can be referenced in a SQL statement within a trigger.
Variables in triggers cannot be declared using the LONG
datatype.
:NEW
and :OLD
cannot be used with LONG
columns.
You can use Oracle Call Interface functions to retrieve a portion of a LONG
value from the database.
The datetime datatypes are DATE
, TIMESTAMP
, TIMESTAMP
WITH
TIME
ZONE
, and TIMESTAMP
WITH
LOCAL
TIME
ZONE
. Values of datetime datatypes are sometimes called "datetimes". The interval datatypes are INTERVAL
YEAR
TO
MONTH
and INTERVAL
DAY
TO
SECOND
. Values of interval datatypes are sometimes called intervals.
Both datetimes and intervals are made up of fields. The values of these fields determine the value of the datatype. Table 2-5 lists the datetime fields and their possible values for datetimes and intervals.
To avoid unexpected results in your DML operations on datetime data, you can verify the database and session time zones by querying the built-in SQL functions DBTIMEZONE
and SESSIONTIMEZONE
. If the time zones have not been set manually, Oracle Database uses the operating system time zone by default. If the operating system time zone is not a valid Oracle time zone, then Oracle uses UTC as the default value.
Table 2-5 Datetime Fields and Values
Datetime Field | Valid Values for Datetime | Valid Values for INTERVAL |
---|---|---|
YEAR |
-4712 to 9999 (excluding year 0) | Any positive or negative integer |
MONTH |
01 to 12 | 0 to 11 |
DAY |
01 to 31 (limited by the values of MONTH and YEAR , according to the rules of the current NLS calendar parameter) |
Any positive or negative integer |
HOUR |
00 to 23 | 0 to 23 |
MINUTE |
00 to 59 | 0 to 59 |
SECOND |
00 to 59.9(n), where 9(n) is the precision of time fractional seconds. The 9(n) portion is not applicable for DATE . |
0 to 59.9(n), where 9(n) is the precision of interval fractional seconds |
TIMEZONE_HOUR |
-12 to 14 (This range accommodates daylight saving time changes.) Not applicable for DATE or TIMESTAMP . |
Not applicable |
TIMEZONE_MINUTE
(See note at end of table) |
00 to 59. Not applicable for DATE or TIMESTAMP . |
Not applicable |
TIMEZONE_REGION |
Query the TZNAME column of the V$TIMEZONE_NAMES data dictionary view. Not applicable for DATE or TIMESTAMP . For a complete listing of all timezone regions, refer to Oracle Database Globalization Support Guide. |
Not applicable |
TIMEZONE_ABBR |
Query the TZABBREV column of the V$TIMEZONE_NAMES data dictionary view. Not applicable for DATE or TIMESTAMP . |
Not applicable |
Note: TIMEZONE_HOUR
and TIMEZONE_MINUTE
are specified together and interpreted as an entity in the format +|- hh:mm, with values ranging from -12:59 to +14:00. Please refer to Oracle Data Provider for .NET Developer's Guide for information on specifying time zone values for that API.
The DATE
datatype stores date and time information. Although date and time information can be represented in both character and number datatypes, the DATE
datatype has special associated properties. For each DATE
value, Oracle stores the following information: century, year, month, date, hour, minute, and second.
You can specify a date value as a literal, or you can convert a character or numeric value to a date value with the TO_DATE
function. To specify a date as a literal, you must use the Gregorian calendar. You can specify an ANSI date literal, as shown in this example:
DATE '1998-12-25'
The ANSI date literal contains no time portion, and must be specified in exactly this format ('YYYY-MM-DD
'). Alternatively you can specify an Oracle date value, as in the following example:
TO_DATE('98-DEC-25 17:30','YY-MON-DD HH24:MI')
The default date format for an Oracle date value is specified by the initialization parameter NLS_DATE_FORMAT
. This example date format includes a two-digit number for the day of the month, an abbreviation of the month name, the last two digits of the year, and a 24-hour time designation.
Oracle automatically converts character values that are in the default date format into date values when they are used in date expressions.
If you specify a date value without a time component, then the default time is midnight (00:00:00 or 12:00:00 for 24-hour and 12-hour clock time, respectively). If you specify a date value without a date, then the default date is the first day of the current month.
Oracle DATE
columns always contain both the date and time fields. Therefore, if you query a DATE
column, then you must either specify the time field in your query or ensure that the time fields in the DATE
column are set to midnight. Otherwise, Oracle may not return the query results you expect. You can use the TRUNC
(date) function to set the time field to midnight, or you can include a greater-than or less-than condition in the query instead of an equality or inequality condition.
Here are some examples that assume a table my_table
with a number column row_num
and a DATE
column datecol
:
INSERT INTO my_table VALUES (1, SYSDATE); INSERT INTO my_table VALUES (2, TRUNC(SYSDATE)); SELECT * FROM my_table; ROW_NUM DATECOL ---------- --------- 1 03-OCT-02 2 03-OCT-02 SELECT * FROM my_table WHERE datecol = TO_DATE('03-OCT-02','DD-MON-YY'); ROW_NUM DATECOL ---------- --------- 2 03-OCT-02 SELECT * FROM my_table WHERE datecol > TO_DATE('02-OCT-02', 'DD-MON-YY'); ROW_NUM DATECOL ---------- --------- 1 03-OCT-02 2 03-OCT-02
If you know that the time fields of your DATE
column are set to midnight, then you can query your DATE
column as shown in the immediately preceding example, or by using the DATE
literal:
SELECT * FROM my_table WHERE datecol = DATE '2002-10-03';
However, if the DATE
column contains values other than midnight, then you must filter out the time fields in the query to get the correct result. For example:
SELECT * FROM my_table WHERE TRUNC(datecol) = DATE '2002-10-03';
Oracle applies the TRUNC
function to each row in the query, so performance is better if you ensure the midnight value of the time fields in your data. To ensure that the time fields are set to midnight, use one of the following methods during inserts and updates:
Use the TO_DATE
function to mask out the time fields:
INSERT INTO my_table VALUES (3, TO_DATE('3-OCT-2002','DD-MON-YYYY'));
Use the DATE
literal:
INSERT INTO my_table VALUES (4, '03-OCT-02');
Use the TRUNC
function:
INSERT INTO my_table VALUES (5, TRUNC(SYSDATE));
The date function SYSDATE
returns the current system date and time. The function CURRENT_DATE
returns the current session date. For information on SYSDATE
, the TO_*
datetime functions, and the default date format, see "Datetime Functions ".
A Julian day number is the number of days since January 1, 4712 BC. Julian days allow continuous dating from a common reference. You can use the date format model "J" with date functions TO_DATE
and TO_CHAR
to convert between Oracle DATE
values and their Julian equivalents.
Note: Oracle Database uses the astronomical system of calculating Julian days, in which the year 4713 BC is specified as -4712. The historical system of calculating Julian days, in contrast, specifies 4713 BC as -4713. If you are comparing Oracle Julian days with values calculated using the historical system, then take care to allow for the 365-day difference in BC dates. For more information, seehttp://aa.usno.navy.mil/faq/docs/millennium.html . |
This statement returns the Julian equivalent of January 1, 1997:
SELECT TO_CHAR(TO_DATE('01-01-1997', 'MM-DD-YYYY'),'J') FROM DUAL; TO_CHAR -------- 2450450
The TIMESTAMP
datatype is an extension of the DATE
datatype. It stores the year, month, and day of the DATE
datatype, plus hour, minute, and second values. This datatype is useful for storing precise time values. Specify the TIMESTAMP
datatype as follows:
TIMESTAMP [(fractional_seconds_precision)]
where fractional_seconds_precision
optionally specifies the number of digits Oracle stores in the fractional part of the SECOND
datetime field. When you create a column of this datatype, the value can be a number in the range 0 to 9. The default is 6. When you specify TIMESTAMP
as a literal, the fractional_seconds_precision
value can be any number of digits up to 9, as follows:
TIMESTAMP'1997-01-31 09:26:50.124'
TIMESTAMP
WITH
TIME
ZONE
is a variant of TIMESTAMP
that includes a time zone offset in its value. The time zone offset is the difference (in hours and minutes) between local time and UTC (Coordinated Universal Time—formerly Greenwich Mean Time). This datatype is useful for collecting and evaluating date information across geographic regions.
Specify the TIMESTAMP
WITH
TIME
ZONE
datatype as follows:
TIMESTAMP [(fractional_seconds_precision)] WITH TIME ZONE
where fractional_seconds_precision
optionally specifies the number of digits Oracle stores in the fractional part of the SECOND
datetime field. When you create a column of this datatype, the value can be a number in the range 0 to 9. The default is 6. When you specify TIMESTAMP
WITH
TIME
ZONE
as a literal, the fractional_seconds_precision
value can be any number of digits up to 9. For example:
TIMESTAMP '1997-01-31 09:26:56.66 +02:00'
Two TIMESTAMP
WITH
TIME
ZONE
values are considered identical if they represent the same instant in UTC, regardless of the TIME
ZONE
offsets stored in the data. For example,
TIMESTAMP '1999-04-15 8:00:00 -8:00'
is the same as
TIMESTAMP '1999-04-15 11:00:00 -5:00'
That is, 8:00 a.m. Pacific Standard Time is the same as 11:00 a.m. Eastern Standard Time.
You can replace the UTC offset with the TZR
(time zone region) format element. For example, the following example has the same value as the preceding example:
TIMESTAMP '1999-04-15 8:00:00 US/Pacific'
To eliminate the ambiguity of boundary cases when the daylight saving time switches, use both the TZR
and a corresponding TZD
format element. The following example ensures that the preceding example will return a daylight saving time value:
TIMESTAMP '1999-10-29 01:30:00 US/Pacific PDT'
If you do not add the TZD
format element, and the datetime value is ambiguous, then Oracle returns an error if you have the ERROR_ON_OVERLAP_TIME
session parameter set to TRUE
. If that parameter is set to FALSE
, then Oracle interprets the ambiguous datetime as standard time.
Oracle time zone data is derived from the public domain information available at ftp://elsie.nci.nih.gov/pub/
. Oracle time zone data may not reflect the most recent data available at this site.
See Also:
|
TIMESTAMP
WITH
LOCAL
TIME
ZONE
is another variant of TIMESTAMP
that includes a time zone offset in its value. It differs from TIMESTAMP
WITH
TIME
ZONE
in that data stored in the database is normalized to the database time zone, and the time zone offset is not stored as part of the column data. When a user retrieves the data, Oracle returns it in the user's local session time zone. The time zone offset is the difference (in hours and minutes) between local time and UTC (Coordinated Universal Time—formerly Greenwich Mean Time). This datatype is useful for displaying date information in the time zone of the client system in a two-tier application.
Specify the TIMESTAMP
WITH
LOCAL
TIME
ZONE
datatype as follows:
TIMESTAMP [(fractional_seconds_precision)] WITH LOCAL TIME ZONE
where fractional_seconds_precision
optionally specifies the number of digits Oracle stores in the fractional part of the SECOND
datetime field. When you create a column of this datatype, the value can be a number in the range 0 to 9. The default is 6.
There is no literal for TIMESTAMP
WITH
LOCAL
TIME
ZONE
.
Oracle time zone data is derived from the public domain information available at ftp://elsie.nci.nih.gov/pub/
. Oracle time zone data may not reflect the most recent data available at this site.
See Also:
|
INTERVAL
YEAR
TO
MONTH
stores a period of time using the YEAR
and MONTH
datetime fields. This datatype is useful for representing the precise difference between two datetime values.
Specify INTERVAL
YEAR
TO
MONTH
as follows:
INTERVAL YEAR [(year_precision)] TO MONTH
where year_precision
is the number of digits in the YEAR
datetime field. The default value of year_precision
is 2.
You have a great deal of flexibility when specifying interval values as literals. Please refer to "Interval Literals" for detailed information on specify interval values as literals.
INTERVAL
DAY
TO
SECOND
stores a period of time in terms of days, hours, minutes, and seconds. This datatype is useful for representing the difference between two datetime values when only the year and month values are significant.
Specify this datatype as follows:
INTERVAL DAY [(day_precision)] TO SECOND [(fractional_seconds_precision)]
where
day_precision
is the number of digits in the DAY
datetime field. Accepted values are 0 to 9. The default is 2.
fractional_seconds_precision
is the number of digits in the fractional part of the SECOND
datetime field. Accepted values are 0 to 9. The default is 6.
You have a great deal of flexibility when specifying interval values as literals. Please refer to "Interval Literals" for detailed information on specify interval values as literals.
You can perform a number of arithmetic operations on date (DATE
), timestamp (TIMESTAMP
, TIMESTAMP
WITH
TIME
ZONE
, and TIMESTAMP
WITH
LOCAL
TIME
ZONE
) and interval (INTERVAL
DAY
TO
SECOND
and INTERVAL
YEAR
TO
MONTH
) data. Oracle calculates the results based on the following rules:
You can use NUMBER
constants in arithmetic operations on date and timestamp values, but not interval values. Oracle internally converts timestamp values to date values and interprets NUMBER
constants in arithmetic datetime and interval expressions as numbers of days. For example, SYSDATE
+ 1 is tomorrow. SYSDATE
- 7 is one week ago. SYSDATE
+ (10/1440) is ten minutes from now. Subtracting the hiredate
column of the sample table employees
from SYSDATE
returns the number of days since each employee was hired. You cannot multiply or divide date or timestamp values.
Oracle implicitly converts BINARY_FLOAT
and BINARY_DOUBLE
operands to NUMBER
.
Each DATE
value contains a time component, and the result of many date operations include a fraction. This fraction means a portion of one day. For example, 1.5 days is 36 hours. These fractions are also returned by Oracle built-in functions for common operations on DATE
data. For example, the MONTHS_BETWEEN
function returns the number of months between two dates. The fractional portion of the result represents that portion of a 31-day month.
If one operand is a DATE
value or a numeric value (neither of which contains time zone or fractional seconds components), then:
Oracle implicitly converts the other operand to DATE
data. (The exception is multiplication of a numeric value times an interval, which returns an interval.)
If the other operand has a time zone value, then Oracle uses the session time zone in the returned value.
If the other operand has a fractional seconds value, then the fractional seconds value is lost.
When you pass a timestamp, interval, or numeric value to a built-in function that was designed only for the DATE
datatype, Oracle implicitly converts the non-DATE
value to a DATE
value. Please refer to "Datetime Functions " for information on which functions cause implicit conversion to DATE
.
Oracle performs all timestamp arithmetic in UTC time. For TIMESTAMP
WITH
LOCAL
TIME
ZONE
, Oracle converts the datetime value from the database time zone to UTC and converts back to the database time zone after performing the arithmetic. For TIMESTAMP
WITH
TIME
ZONE
, the datetime value is always in UTC, so no conversion is necessary.
Table 2-6 is a matrix of datetime arithmetic operations. Dashes represent operations that are not supported.
Table 2-6 Matrix of Datetime Arithmetic
Operand & Operator | DATE | TIMESTAMP | INTERVAL | Numeric |
---|---|---|---|---|
DATE | ||||
+ | -- |
-- |
DATE |
DATE |
- | DATE |
DATE |
DATE |
DATE |
* | -- |
-- |
-- |
-- |
/ | -- |
-- |
-- |
-- |
TIMESTAMP | ||||
+ | -- |
-- |
TIMESTAMP |
-- |
- | INTERVAL |
INTERVAL |
TIMESTAMP |
TIMESTAMP |
* | -- |
-- |
-- |
-- |
/ | -- |
-- |
-- |
-- |
INTERVAL | ||||
+ | DATE |
TIMESTAMP |
INTERVAL |
-- |
- | -- |
-- |
INTERVAL |
-- |
* | -- |
-- |
-- |
INTERVAL |
/ | -- |
-- |
-- |
INTERVAL |
Numeric | ||||
+ | DATE |
DATE |
-- |
NA |
- | -- |
-- |
-- |
NA |
* | -- |
-- |
INTERVAL |
NA |
/ | -- |
-- |
-- |
NA |
You can add an interval value expression to a start time. Consider the sample table oe.orders
with a column order_date
. The following statement adds 30 days to the value of the order_date
column:
SELECT order_id, order_date + INTERVAL '30' DAY FROM orders;
Oracle Database automatically determines, for any given time zone region, whether daylight saving is in effect and returns local time values accordingly. The datetime value is sufficient for Oracle to determine whether daylight saving time is in effect for a given region in all cases except boundary cases. A boundary case occurs during the period when daylight saving goes into or comes out of effect. For example, in the US-Pacific region, when daylight saving goes into effect, the time changes from 2:00 a.m. to 3:00 a.m. The one hour interval between 2 and 3 a.m. does not exist. When daylight saving goes out of effect, the time changes from 2:00 a.m. back to 1:00 a.m., and the one-hour interval between 1 and 2 a.m. is repeated.
To resolve these boundary cases, Oracle uses the TZR
and TZD
format elements, as described in Table 2-16. TZR
represents the time zone region in datetime input strings. Examples are 'Australia/North
', 'UTC
', and 'Singapore
'. TZD
represents an abbreviated form of the time zone region with daylight saving information. Examples are 'PST
' for US/Pacific standard time and 'PDT
' for US/Pacific daylight time. To see a listing of valid values for the TZR
and TZD
format elements, query the TZNAME
and TZABBREV
columns of the V$TIMEZONE_NAMES
dynamic performance view.
Timezone region names are needed by the daylight saving feature. The region names are stored in two time zone files. The default time zone file is a small file containing only the most common time zones to maximize performance. If your time zone is not in the default file, then you will not have daylight saving support until you provide a path to the complete (larger) file by way of the ORA_TZFILE
environment variable. Please refer to Oracle Database Administrator's Guide for more information about setting the ORA_TZFILE
environment variable. For a complete listing of the timezone region names in both files, please refer to Oracle Database Globalization Support Guide.
Oracle time zone data is derived from the public domain information available at ftp://elsie.nci.nih.gov/pub/
. Oracle time zone data may not reflect the most recent data available at this site.
See Also:
|
The following example shows how to declare some datetime and interval datatypes.
CREATE TABLE time_table ( start_time TIMESTAMP, duration_1 INTERVAL DAY (6) TO SECOND (5), duration_2 INTERVAL YEAR TO MONTH);
The start_time
column is of type TIMESTAMP
. The implicit fractional seconds precision of TIMESTAMP
is 6.
The duration_1
column is of type INTERVAL
DAY
TO
SECOND
. The maximum number of digits in field DAY
is 6 and the maximum number of digits in the fractional second is 5. The maximum number of digits in all other datetime fields is 2.
The duration_2
column is of type INTERVAL
YEAR
TO
MONTH
. The maximum number of digits of the value in each field (YEAR
and MONTH
) is 2.
The RAW
and LONG
RAW
datatypes store data that is not to be interpreted (that is, not explicitly converted when moving data between different systems) by Oracle Database. These datatypes are intended for binary data or byte strings. For example, you can use LONG
RAW
to store graphics, sound, documents, or arrays of binary data, for which the interpretation is dependent on the use.
Oracle strongly recommends that you convert LONG
RAW
columns to binary LOB (BLOB
) columns. LOB columns are subject to far fewer restrictions than LONG
columns. See TO_LOB for more information.
RAW
is a variable-length datatype like VARCHAR2
, except that Oracle Net (which connects user sessions to the instance) and the Import and Export utilities do not perform character conversion when transmitting RAW
or LONG
RAW
data. In contrast, Oracle Net and Import/Export automatically convert CHAR
, VARCHAR2
, and LONG
data from the database character set to the user session character set (which you can set with the NLS_LANGUAGE
parameter of the ALTER
SESSION
statement), if the two character sets are different.
When Oracle automatically converts RAW
or LONG
RAW
data to and from CHAR
data, the binary data is represented in hexadecimal form, with one hexadecimal character representing every four bits of RAW
data. For example, one byte of RAW
data with bits 11001011 is displayed and entered as CB
.
The built-in LOB datatypes BLOB
, CLOB
, and NCLOB
(stored internally) and BFILE
(stored externally) can store large and unstructured data such as text, image, video, and spatial data. BLOB
, CLOB
, and NCLOB
data can be up to (4 gigabytes -1) * (database block size) in size. BFILE
data can be up to 4 gigabytes in size.
When creating a table, you can optionally specify different tablespace and storage characteristics for LOB columns or LOB object attributes from those specified for the table.
LOB columns contain LOB locators that can refer to in-line (in the database) or out-of-line (outside the database) LOB values. Selecting a LOB from a table actually returns the LOB locator and not the entire LOB value. The DBMS_LOB
package and Oracle Call Interface (OCI) operations on LOBs are performed through these locators.
LOBs are similar to LONG
and LONG
RAW
types, but differ in the following ways:
LOBs can be attributes of an object type (user-defined datatype).
The LOB locator is stored in the table column, either with or without the actual LOB value. BLOB
, NCLOB
, and CLOB
values can be stored in separate tablespaces. BFILE
data is stored in an external file on the server.
When you access a LOB column, the locator is returned.
A LOB can be up to (4 gigabytes - 1)*(database block size) in size. BFILE
maximum size is operating system dependent but cannot exceed 4 gigabytes.
LOBs permit efficient, random, piece-wise access to and manipulation of data.
You can define more than one LOB column in a table.
With the exception of NCLOB
, you can define one or more LOB attributes in an object.
You can declare LOB bind variables.
You can select LOB columns and LOB attributes.
You can insert a new row or update an existing row that contains one or more LOB columns or an object with one or more LOB attributes. In update operations, you can set the internal LOB value to NULL
, empty, or replace the entire LOB with data. You can set the BFILE
to NULL
or make it point to a different file.
You can update a LOB row-column intersection or a LOB attribute with another LOB row-column intersection or LOB attribute.
You can delete a row containing a LOB column or LOB attribute and thereby also delete the LOB value. For BFILEs, the actual operating system file is not deleted.
You can access and populate rows of an in-line LOB column (a LOB column stored in the database) simply by issuing an INSERT
or UPDATE
statement. However, to access and populate a LOB attribute that is part of an object type, you must first initialize the LOB attribute using the EMPTY_CLOB
or EMPTY_BLOB
function. You can then select the empty LOB attribute and populate it using the DBMS_LOB
package or some other appropriate interface.
LOB columns are subject to the following restrictions:
You cannot specify a LOB as a primary key column.
Distributed LOBs are not supported. Therefore, you cannot use a remote locator in SELECT
or WHERE
clauses of queries or in functions of the DBMS_LOB
package.
The following syntax is not supported for LOBs:
SELECT lobcol FROM table1@remote_site; INSERT INTO lobtable SELECT type1.lobattr FROM table1@remote_site; SELECT DBMS_LOB.getlength(lobcol) FROM table1@remote_site;
However, you can use a remote locator in others parts of queries that reference LOBs. The following syntax is supported on remote LOB columns:
CREATE TABLE t AS SELECT * FROM table1@remote_site; INSERT INTO t SELECT * FROM table1@remote_site; UPDATE t SET lobcol = (SELECT lobcol FROM table1@remote_site); INSERT INTO table1@remote_site ... UPDATE table1@remote_site ... DELETE FROM table1@remote_site ...
For the first three types of statement, which contain subqueries, only standalone LOB columns are allowed in the select list. SQL functions or DBMS_LOB
APIs on LOBs are not supported. For example, the following statement is supported:
CREATE TABLE AS SELECT clob_col FROM tab@dbs2;
However, the following statement is not supported:
CREATE TABLE AS SELECT dbms_lob.substr(clob_col) from tab@dbs2;
Clusters cannot contain LOBs, either as key or non-key columns.
The following data structures are supported only as temporary instances. You cannot store these instances in database tables:
Varray of any LOB type
Varray of any type containing a LOB type, such as an ADT with a LOB attribute.
You cannot specify LOB columns in the ORDER
BY
clause of a query, or in the GROUP
BY
clause of a query or in an aggregate function.
You cannot specify a LOB column in a SELECT
... DISTINCT
or SELECT
... UNIQUE
statement or in a join. However, you can specify a LOB attribute of an object type column in a SELECT
... DISTINCT
statement or in a query that uses the UNION
or MINUS
set operator if the column's object type has a MAP
or ORDER
function defined on it.
You cannot specify LOB columns in ANALYZE
... COMPUTE
or ANALYZE
... ESTIMATE
statements.
The first (INITIAL
) extent of a LOB segment must contain at least three database blocks.
When creating an UPDATE
DML trigger, you cannot specify a LOB column in the UPDATE
OF
clause.
You cannot specify a LOB column as part of an index key. However, you can specify a LOB column in the function of a function-based index or in the indextype specification of a domain index. In addition, Oracle Text lets you define an index on a CLOB
column.
In an INSERT
or UPDATE
operation, you can bind data of any size to a LOB column, but you cannot bind data to a LOB attribute of an object type. In an INSERT
... AS
SELECT
operation, you can bind up to 4000 bytes of data to LOB columns.
If a table has both LONG
and LOB columns, you cannot bind more than 4000 bytes of data to both the LONG
and LOB columns in the same SQL statement. However, you can bind more than 4000 bytes of data to either the LONG
or the LOB column.
Note: For a table on which you have defined a DML trigger, if you use OCI functions orDBMS_LOB routines to change the value of a LOB column or the LOB attribute of an object type column, Oracle does not fire the DML trigger. |
See Also:
|
The following example shows how the sample table pm.print_media
was created. (This example assumes the existence of the textdoc_tab
object table, which is nested table in the print_media
table.)
CREATE TABLE print_media ( product_id NUMBER(6) , ad_id NUMBER(6) , ad_composite BLOB , ad_sourcetext CLOB , ad_finaltext CLOB , ad_fltextn NCLOB , ad_textdocs_ntab textdoc_tab , ad_photo BLOB , ad_graphic BFILE , ad_header adheader_typ ) NESTED TABLE ad_textdocs_ntab STORE AS textdocs_nestedtab;
See Also:
|
The BFILE
datatype enables access to binary file LOBs that are stored in file systems outside Oracle Database. A BFILE
column or attribute stores a BFILE
locator, which serves as a pointer to a binary file on the server file system. The locator maintains the directory name and the filename.
You can change the filename and path of a BFILE
without affecting the base table by using the BFILENAME
function. Please refer to BFILENAME for more information on this built-in SQL function.
Binary file LOBs do not participate in transactions and are not recoverable. Rather, the underlying operating system provides file integrity and durability. The maximum file size supported is 4 gigabytes.
The database administrator must ensure that the external file exists and that Oracle processes have operating system read permissions on the file.
The BFILE
datatype enables read-only support of large binary files. You cannot modify or replicate such a file. Oracle provides APIs to access file data. The primary interfaces that you use to access file data are the DBMS_LOB
package and the Oracle Call Interface (OCI).
See Also: Oracle Database Application Developer's Guide - Large Objects and Oracle Call Interface Programmer's Guide for more information about LOBs and CREATE DIRECTORY |
The BLOB
datatype stores unstructured binary large objects. BLOB
objects can be thought of as bitstreams with no character set semantics. BLOB
objects can store up to (4 gigabytes-1) * (database block size) of binary data.
BLOB
objects have full transactional support. Changes made through SQL, the DBMS_LOB
package, or the Oracle Call Interface (OCI) participate fully in the transaction. BLOB
value manipulations can be committed and rolled back. However, you cannot save a BLOB
locator in a PL/SQL or OCI variable in one transaction and then use it in another transaction or session.
The CLOB
datatype stores single-byte and multibyte character data. Both fixed-width and variable-width character sets are supported, and both use the database character set. CLOB
objects can store up to (4 gigabytes-1) * (database block size) of character data.
CLOB
objects have full transactional support. Changes made through SQL, the DBMS_LOB
package, or the Oracle Call Interface (OCI) participate fully in the transaction. CLOB
value manipulations can be committed and rolled back. However, you cannot save a CLOB
locator in a PL/SQL or OCI variable in one transaction and then use it in another transaction or session.
The NCLOB
datatype stores Unicode data. Both fixed-width and variable-width character sets are supported, and both use the national character set. NCLOB
objects can store up to (4 gigabytes-1) * (database block size) of character text data.
NCLOB
objects have full transactional support. Changes made through SQL, the DBMS_LOB
package, or the OCI participate fully in the transaction. NCLOB
value manipulations can be committed and rolled back. However, you cannot save an NCLOB
locator in a PL/SQL or OCI variable in one transaction and then use it in another transaction or session.
Each row in the database has an address. You can examine a row address by querying the pseudocolumn ROWID
. Values of this pseudocolumn are strings representing the address of each row. These strings have the datatype ROWID
. You can also create tables and clusters that contain actual columns having the ROWID
datatype. Oracle Database does not guarantee that the values of such columns are valid rowids. Please refer to Chapter 3, " Pseudocolumns" for more information on the ROWID
pseudocolumn.
Beginning with Oracle8, Oracle SQL incorporated an extended format for rowids to efficiently support partitioned tables and indexes and tablespace-relative data block addresses (DBAs) without ambiguity.
Character values representing rowids in Oracle7 and earlier releases are called restricted rowids. Their format is as follows:
block.row.file
block
is a hexadecimal string identifying the data block of the datafile containing the row. The length of this string depends on your operating system.
row
is a four-digit hexadecimal string identifying the row in the data block. The first row of the block has a digit of 0.
file
is a hexadecimal string identifying the database file containing the row. The first datafile has the number 1. The length of this string depends on your operating system.
The extended ROWID
datatype stored in a user column includes the data in the restricted rowid plus a data object number. The data object number is an identification number assigned to every database segment. You can retrieve the data object number from the data dictionary views USER_OBJECTS
, DBA_OBJECTS
, and ALL_OBJECTS
. Objects that share the same segment (clustered tables in the same cluster, for example) have the same object number.
Extended rowids are stored as base 64 values that can contain the characters A-Z, a-z, 0-9, and the plus sign (+) and forward slash (/). Extended rowids are not available directly. You can use a supplied package, DBMS_ROWID
, to interpret extended rowid contents. The package functions extract and provide information that would be available directly from a restricted rowid as well as information specific to extended rowids.
See Also: PL/SQL Packages and Types Reference for information on the functions available with theDBMS_ROWID package and how to use them |
The restricted form of a rowid is still supported in this release for backward compatibility, but all tables return rowids in the extended format.
See Also: Oracle Database Upgrade Guide for information regarding compatibility and migration issues |
Each row in a database has an address. However, the rows of some tables have addresses that are not physical or permanent or were not generated by Oracle Database. For example, the row addresses of index-organized tables are stored in index leaves, which can move. Rowids of foreign tables (such as DB2 tables accessed through a gateway) are not standard Oracle rowids.
Oracle uses universal rowids (urowids) to store the addresses of index-organized and foreign tables. Index-organized tables have logical urowids and foreign tables have foreign urowids. Both types of urowid are stored in the ROWID
pseudocolumn (as are the physical rowids of heap-organized tables).
Oracle creates logical rowids based on the primary key of the table. The logical rowids do not change as long as the primary key does not change. The ROWID
pseudocolumn of an index-organized table has a datatype of UROWID
. You can access this pseudocolumn as you would the ROWID
pseudocolumn of a heap-organized table (that is, using a SELECT
... ROWID
statement). If you wish to
store the rowids of an index-organized table, then you can define a column of type UROWID
for the table and retrieve the value of the ROWID
pseudocolumn into that column.
Note: Heap-organized tables have physical rowids. Oracle does not recommend that you specify a column of datatypeUROWID for a heap-organized table. |
See Also: Oracle Database Concepts for more information on universal rowids and "ROWID Datatype " for a discussion of the address of database rows |
SQL statements that create tables and clusters can also use ANSI datatypes and datatypes from the IBM products SQL/DS and DB2. Oracle recognizes the ANSI or IBM datatype name that differs from the Oracle Database datatype name, records it as the name of the datatype of the column, and then stores the column data in an Oracle datatype based on the conversions shown in the tables that follow.
Table 2-7 ANSI Datatypes Converted to Oracle Datatypes
ANSI SQL Datatype | ANSI SQL Datatype | Notes |
---|---|---|
CHARACTER(n)
CHAR(n) |
CHAR(n) | |
CHARACTER VARYING(n)
CHAR VARYING(n) |
VARCHAR(n) | |
NATIONAL CHARACTER(n)
NATIONAL CHAR(n) NCHAR(n) |
NCHAR(n) | |
NATIONAL CHARACTER VARYING(n)
NATIONAL CHAR VARYING(n) NCHAR VARYING(n) |
NVARCHAR2(n) | |
NUMERIC(p,s)
DECIMAL(p,s)a |
NUMBER(p,s) | aThe NUMBERIC and DECIMAL datatypes can specify only fixed-point numbers. For those datatypes, s defaults to 0. |
INTEGER
INT SMALLINT |
NUMBER(38) | |
FLOAT(b)b
DOUBLE PRECISIONc REALd |
NUMBER | bThe FLOAT datatype is a floating-point number with a binary precision b. The default precision for this datatypes is 126 binary, or 38 decimal.
cThe DOUBLE PRECISION datatype is a floating-point number with binary precision 126. dThe REAL datatype is a floating-point number with a binary precision of 63, or 18 decimal. |
Table 2-8 SQL/DS and DB2 Datatypes Converted to Oracle Datatypes
SQL/DS or DB2 Datatype | Oracle Datatype |
---|---|
CHARACTER(n) |
CHAR(n) |
VARCHAR(n) |
VARCHAR(n) |
LONG VARCHAR(n) |
LONG |
DECIMAL(p,s) (Note 1) |
NUMBER(p,s) |
INTEGER
|
NUMBER(38) |
FLOAT(b) (Note 2) |
NUMBER |
Note 1: The DECIMAL
datatype can specify only fixed-point numbers. For this datatype, s
defaults to 0.
Note 2: The FLOAT
datatype is a floating-point number with a binary precision b
. The default precision for this datatype is 126 binary or 38 decimal.
Do not define columns with the following SQL/DS and DB2 datatypes, because they have no corresponding Oracle datatype:
GRAPHIC
LONG
VARGRAPHIC
VARGRAPHIC
TIME
Note that data of type TIME
can also be expressed as Oracle datetime data.
User-defined datatypes use Oracle built-in datatypes and other user-defined datatypes as the building blocks of object types that model the structure and behavior of data in applications. The sections that follow describe the various categories of user-defined types.
See Also:
|
Object types are abstractions of the real-world entities, such as purchase orders, that application programs deal with. An object type is a schema object with three kinds of components:
A name, which identifies the object type uniquely within that schema
Attributes, which are built-in types or other user-defined types. Attributes model the structure of the real-world entity.
Methods, which are functions or procedures written in PL/SQL and stored in the database, or written in a language like C or Java and stored externally. Methods implement operations the application can perform on the real-world entity.
An object identifier (OID) uniquely identifies an object and enables you to reference the object from other objects or from relational tables. A datatype category called REF
represents such references. A REF
is a container for an object identifier. REF
s are pointers to objects.
When a REF
value points to a nonexistent object, the REF
is said to be "dangling". A dangling REF
is different from a null REF
. To determine whether a REF
is dangling or not, use the condition IS
[NOT
] DANGLING
. For example, given object view oc_orders
in the sample schema oe
, the column customer_ref
is of type REF
to type customer_typ
, which has an attribute cust_email
:
SELECT o.customer_ref.cust_email FROM oc_orders o WHERE o.customer_ref IS NOT DANGLING;
An array is an ordered set of data elements. All elements of a given array are of the same datatype. Each element has an index, which is a number corresponding to the position of the element in the array.
The number of elements in an array is the size of the array. Oracle arrays are of variable size, which is why they are called varrays. You must specify a maximum size when you declare the varray.
When you declare a varray, it does not allocate space. It defines a type, which you can use as:
The datatype of a column of a relational table
An object type attribute
A PL/SQL variable, parameter, or function return type
Oracle normally stores an array object either in line (that is, as part of the row data) or out of line (in a LOB), depending on its size. However, if you specify separate storage characteristics for a varray, then Oracle stores it out of line, regardless of its size. Please refer to the varray_col_properties of CREATE TABLE for more information about varray storage.
A nested table type models an unordered set of elements. The elements may be built-in types or user-defined types. You can view a nested table as a single-column table or, if the nested table is an object type, as a multicolumn table, with a column for each attribute of the object type.
A nested table definition does not allocate space. It defines a type, which you can use to declare:
The datatype of a column of a relational table
An object type attribute
A PL/SQL variable, parameter, or function return type
When a nested table appears as the type of a column in a relational table or as an attribute of the underlying object type of an object table, Oracle stores all of the nested table data in a single table, which it associates with the enclosing relational or object table.
Oracle provides SQL-based interfaces for defining new types when the built-in or ANSI-supported types are not sufficient. The behavior for these types can be implemented in C/C++, Java, or PL/ SQL. Oracle Database automatically provides the low-level infrastructure services needed for input-output, heterogeneous client-side access for new datatypes, and optimizations for data transfers between the application and the database.
These interfaces can be used to build user-defined (or object) types and are also used by Oracle to create some commonly useful datatypes. Several such datatypes are supplied with the server, and they serve both broad horizontal application areas (for example, the Any
types) and specific vertical ones (for example, the spatial types).
The Oracle-supplied types, along with cross-references to the documentation of their implementation and use, are described in the following sections:
The Any
types provide highly flexible modeling of procedure parameters and table columns where the actual type is not known. These datatypes let you dynamically encapsulate and access type descriptions, data instances, and sets of data instances of any other SQL type. These types have OCI and PL/SQL interfaces for construction and access.
This type can contain a type description of any named SQL type or unnamed transient type.
This type contains an instance of a given type, with data, plus a description of the type. ANYDATA
can be used as a table column datatype and lets you store heterogeneous values in a single column. The values can be of SQL built-in types as well as user-defined types.
This type contains a description of a given type plus a set of data instances of that type. ANYDATASET
can be used as a procedure parameter datatype where such flexibility is needed. The values of the data instances can be of SQL built-in types as well as user-defined types.
See Also: PL/SQL Packages and Types Reference for information on theAnyType , AnyData , and AnyDataSet types |
Extensible Markup Language (XML) is a standard format developed by the World Wide Web Consortium (W3C) for representing structured and unstructured data on the World Wide Web. Universal resource identifiers (URIs) identify resources such as Web pages anywhere on the Web. Oracle provides types to handle XML and URI data, as well as a class of URIs called DBURIRef
s to access data stored within the database itself. It also provides a new set of types to store and access both external and internal URIs from within the database.
This Oracle-supplied type can be used to store and query XML data in the database. XMLType
has member functions you can use to access, extract, and query the XML data using XPath expressions. XPath is another standard developed by the W3C committee to traverse XML documents. Oracle XMLType
functions support many W3C XPath expressions. Oracle also provides a set of SQL functions and PL/SQL packages to create XMLType
values from existing relational or object-relational data.
XMLType
is a system-defined type, so you can use it as an argument of a function or as the datatype of a table or view column. You can also create tables and views of XMLType
. When you create an XMLType
column in a table, you can choose to store the XML data in a CLOB
column or object relationally.
You can also register the schema (using the DBMS_XMLSCHEMA
package) and create a table or column conforming to the registered schema. In this case Oracle stores the XML data in underlying object-relational columns by default, but you can specify storage in a CLOB
column even for schema-based data.
Queries and DML on XMLType
columns operate the same regardless of the storage mechanism.
Oracle supplies a family of URI types—URIType
, DBURIType
, XDBURIType
, and HTTPURIType
—which are related by an inheritance hierarchy. URIType
is an object type and the others are subtypes of URIType
. Since URIType
is the supertype, you can create columns of this type and store DBURIType
or HTTPURIType
type instances in this column.
You can use HTTPURIType
to store URLs to external Web pages or to files. Oracle accesses these files using HTTP (Hypertext Transfer Protocol).
You can use XDBURIType
to expose documents in the XML database hierarchy as URIs that can be embedded in any URIType
column in a table. The XDBURIType
consists of a URL, which comprises the hierarchical name of the XML document to which it refers and an optional fragment representing the XPath syntax. The fragment is separated from the URL part by a pound sign (#). The following lines are examples of XDBURIType
:
/home/oe/doc1.xml /home/oe/doc1.xml#/orders/order_item
DBURIType
can be used to store DBURIRef
s, which reference data inside the database. Storing DBURIRef
s lets you reference data stored inside or outside the database and access the data consistently.
DBURIRef
s use an XPath-like representation to reference data inside the database. If you imagine the database as an XML tree, then you would see the tables, rows, and columns as elements in the XML document. For example, the sample human resources user hr
would see the following XML tree:
<HR> <EMPLOYEES> <ROW> <EMPLOYEE_ID>205</EMPLOYEE_ID> <LAST_NAME>Higgins</LAST_NAME> <SALARY>12000</SALARY> .. <!-- other columns --> </ROW> ... <!-- other rows --> </EMPLOYEES> <!-- other tables..--> </HR> <!-- other user schemas on which you have some privilege on..-->
The DBURIRef
is an XPath expression over this virtual XML document. So to reference the SALARY
value in the EMPLOYEES
table for the employee with employee number 205, we can write a DBURIRef
as,
/HR/EMPLOYEES/ROW[EMPLOYEE_ID=205]/SALARY
Using this model, you can reference data stored in CLOB
columns or other columns and expose them as URLs to the external world.
Oracle also provides the URIFactory
package, which can create and return instances of the various subtypes of the URITypes
. The package analyzes the URL string, identifies the type of URL (HTTP, DBURI
, and so on), and creates an instance of the subtype. To create a DBURI
instance, the URL must start with the prefix /oradb
. For example, URIFactory.getURI('/oradb/HR/EMPLOYEES')
would create a DBURIType
instance and URIFactory.getUri('/sys/schema')
would create an XDBURIType
instance.
See Also:
|
Oracle Spatial is designed to make spatial data management easier and more natural to users of location-enabled applications, geographic information system (GIS) applications, and geoimaging applications. Once the spatial data is stored in an Oracle database, you can easily manipulate, retrieve, and relate it to all the other data stored in the database. The following datatypes are not available unless you have installed Oracle Spatial.
The geometric description of a spatial object is stored in a single row, in a single column of object type SDO_GEOMETRY
in a user-defined table. Any table that has a column of type SDO_GEOMETRY
must have another column, or set of columns, that defines a unique primary key for that table. Tables of this sort are sometimes called geometry tables.
The SDO_GEOMETRY
object type has the following definition:
CREATE TYPE SDO_GEOMETRY AS OBJECT ( SDO_GTYPE NUMBER, SDO_SRID NUMBER, SDO_POINT SDO_POINT_TYPE, SDO_ELEM_INFO SDO_ELEM_INFO_ARRAY, SDO_ORDINATES SDO_ORDINATE_ARRAY);
In the GeoRaster object-relational model, a raster grid or image object is stored in a single row, in a single column of object type SDO_GEORASTER
in a user-defined table. Tables of this sort are called GeoRaster tables.
The SDO_GEORASTER
object type has the following definition:
CREATE TYPE SDO_GEORASTER AS OBJECT ( rasterType NUMBER, spatialExtent SDO_GEOMETRY, rasterDataTable VARCHAR2(32), rasterID NUMBER, metadata XMLType);
See Also: Oracle Spatial User's Guide and Reference and Oracle Spatial GeoRaster for information on the full implementation of the spatial datatypes and guidelines for using them |
Oracle interMedia uses object types, similar to Java or C++ classes, to describe multimedia data. An instance of these object types consists of attributes, including metadata and the media data, and methods. The interMedia datatypes are created in the ORDSYS
schema. Public synonyms exist for all the datatypes, so you can access them without specifying the schema name.
See Also: Oracle interMedia Reference for information on the implementation of these types and guidelines for using them |
The ORDImageSignature
object type supports a compact representation of the color, texture, and shape information of image data.
The ORDDOC
object type supports storage and management of any type of media data, including audio, image and video data. Use this type when you want all media to be stored in a single column.
The following datatypes provide compliance with the ISO-IEC 13249-5 Still Image standard, commonly referred to as SQL/MM StillImage.
The SI_StillImage
object type represents digital images with inherent image characteristics such as height, width, and format.
The SI_AverageColor
object type represents a feature that characterizes an image by its average color.
The SI_ColorHistogram
object type represents a feature that characterizes an image by the relative frequencies of the colors exhibited by samples of the raw image.
Given an image divided into n
by m
rectangles, the SI_PositionalColor
object type represents the feature that characterizes an image by the n
by m
most significant colors of the rectangles.
The Oracle Expression Filter allows application developers to manage and evaluate conditional expressions that describe users' interests in data. The Expression Filter includes the following datatype:
Expression Filter uses a virtual datatype called Expression
to manage and evaluate conditional expressions as data in database tables. The Expression Filter creates a column of Expression
datatype from a VARCHAR2
column by assigning an attribute set to the column. This assignment enables a data constraint that ensures the validity of expressions stored in the column.
You can define conditions using the EVALUATE
operator on an Expression
datatype to evaluate the expressions stored in a column for some data. If you are using Enterprise Edition, then you can also define an Expression Filter index on a column of Expression
datatype to process queries using the EVALUATE
operator.
See Also: Oracle Database Application Developer's Guide - Expression Filter for more information on the Expression Filter |