UPDATE

Purpose

Use the UPDATE statement to change existing values in a table or in the base table of a view or the master table of a materialized view.

Additional Topics

• Prerequisites

• Syntax

• Semantics

• Examples

Prerequisites

For you to update values in a table, the table must be in your own schema or you must have the UPDATE object privilege on the table.

For you to update values in the base table of a view:

• You must have the UPDATE object privilege on the view, and

• Whoever owns the schema containing the view must have the UPDATE object privilege on the base table.

The UPDATE ANY TABLE system privilege also allows you to update values in any table or in the base table of any view.

You must also have the SELECT object privilege on the object you want to update if:

• The object is on a remote database or

• The SQL92_SECURITY initialization parameter is set to TRUE and the UPDATE operation references table columns, such as the columns in a where_clause.

Syntax

update::=

Description of the illustration update.gif

(DML_table_expression_clause::=, update_set_clause ::=, where_clause ::=, returning_clause ::=)

DML_table_expression_clause::=

Description of the illustration DML_table_expression_clause.gif

(subquery::=—part of SELECT, subquery_restriction_clause ::=, table_collection_expression ::=)

subquery_restriction_clause ::=

Description of the illustration subquery_restriction_clause.gif


table_collection_expression ::=

Description of the illustration table_collection_expression.gif


update_set_clause ::=

Description of the illustration update_set_clause.gif


where_clause ::=

Description of the illustration where_clause.gif


returning_clause ::=

Description of the illustration returning_clause.gif

Semantics

hint

Specify a comment that passes instructions to the optimizer on choosing an execution plan for the statement.

You can place a parallel hint immediately after the UPDATE keyword to parallelize both the underlying scan and UPDATE operations.

DML_table_expression_clause

The ONLY clause applies only to views. Specify ONLY syntax if the view in the UPDATE clause is a view that belongs to a hierarchy and you do not want to update rows from any of its subviews.

schema

Specify the schema containing the object to be updated. If you omit schema, then the database assumes the object is in your own schema.

table | view | materialized_view |subquery

Specify the name of the table, view, materialized view, or the columns returned by a subquery to be updated. Issuing an UPDATE statement against a table fires any UPDATE triggers associated with the table.

• If you specify view, then the database updates the base table of the view. You cannot update a view except with INSTEAD OF triggers if the defining query of the view contains one of the following constructs:

A set operator

a DISTINCT operator

An aggregate or analytic function

A GROUP BY, ORDER BY, MODEL, CONNECT BY, or START WITH clause

A collection expression in a SELECT list

A subquery in a SELECT list

A subquery designated WITH READ ONLY

Joins, with some exceptions, as documented in Oracle Database Administrator's Guide

• In addition, if the view was created with the WITH CHECK OPTION, then you can update the view only if the resulting data satisfies the view's defining query.

• If table or the base table of view contains one or more domain index columns, then this statement executes the appropriate indextype update routine.

• You cannot update rows in a read-only materialized view. If you update rows in a writable materialized view, then the database updates the rows from the underlying container table. However, the updates are overwritten at the next refresh operation.If you update rows in an updatable materialized view that is part of a materialized view group, then the database also updates the corresponding rows in the master table.

  
  

  See Also: Oracle Data Cartridge Developer's Guide for more information on the indextype update routines CREATE MATERIALIZED VIEW for information on creating updatable materialized views

  
  

PARTITION | SUBPARTITION

Specify the name of the partition or subpartition within table targeted for updates. You need not specify the partition name when updating values in a partitioned table. However in some cases specifying the partition name can be more efficient than a complicated where_clause.

dblink

Specify a complete or partial name of a database link to a remote database where the object is located. You can use a database link to update a remote object only if you are using Oracle Database distributed functionality.

If you omit dblink, then the database assumes the object is on the local database.

subquery_restriction_clause

Use the subquery_restriction_clause to restrict the subquery in one of the following ways:

WITH READ ONLY

Specify WITH READ ONLY to indicate that the table or view cannot be updated.

WITH CHECK OPTION

Specify WITH CHECK OPTION to indicate that Oracle Database prohibits any changes to the table or view that would produce rows that are not included in the subquery. When used in the subquery of a DML statement, you can specify this clause in a subquery in the FROM clause but not in subquery in the WHERE clause.

CONSTRAINT constraint

Specify the name of the CHECK OPTION constraint. If you omit this identifier, then Oracle automatically assigns the constraint a name of the form SYS_Cn, where n is an integer that makes the constraint name unique within the database.

table_collection_expression

The table_collection_expression lets you inform Oracle that the value of collection_expression should be treated as a table for purposes of query and DML operations. The collection_expression can be a subquery, a column, a function, or a collection constructor. Regardless of its form, it must return a collection value—that is, a value whose type is nested table or varray. This process of extracting the elements of a collection is called collection unnesting.

You can use a table_collection_expression to update rows in one table based on rows from another table. For example, you could roll up four quarterly sales tables into a yearly sales table.

t_alias

Specify a correlation name (alias) for the table, view, or subquery to be referenced elsewhere in the statement. This alias is required if the DML_table_expression_clause references any object type attributes or object type methods.

Restrictions on the DML_table_expression_clause

• You cannot execute this statement if table or the base table of view contains any domain indexes marked IN_PROGRESS or FAILED.

• You cannot insert into a partition if any affected index partitions are marked UNUSABLE.

• You cannot specify the order_by_clause in the subquery of the DML_table_expression_clause.

• If you specify an index, index partition, or index subpartition that has been marked UNUSABLE, then the UPDATE statement will fail unless the SKIP_UNUSABLE_INDEXES session parameter has been set to TRUE.

update_set_clause

The update_set_clause lets you set column values.

column

Specify the name of a column of the object that is to be updated. If you omit a column of the table from the update_set_clause, then the value of that column remains unchanged.

If column refers to a LOB object attribute, then you must first initialize it with a value of empty or null. You cannot update it with a literal. Also, if you are updating a LOB value using some method other than a direct UPDATE SQL statement, then you must first lock the row containing the LOB. See for_update_clause for more information.

If column is part of the partitioning key of a partitioned table, then UPDATE will fail if you change a value in the column that would move the row to a different partition or subpartition, unless you enable row movement. Please refer to the row_movement_clause of CREATE TABLE or ALTER TABLE .

In addition, if column is part of the partitioning key of a list-partitioned table, then UPDATE will fail if you specify a value for the column that does not already exist in the partition_value list of one of the partitions.

subquery

Specify a subquery that returns exactly one row for each row updated.

• If you specify only one column in the update_set_clause, then the subquery can return only one value.

• If you specify multiple columns in the update_set_clause, then the subquery must return as many values as you have specified columns.

• If the subquery returns no rows, then the column is assigned a null.

• If this subquery refers to remote objects, then the UPDATE operation can run in parallel as long as the reference does not loop back to an object on the local database. However, if the subquery in the DML_table_expression_clause refers to any remote objects, then the UPDATE operation will run serially without notification.

You can use the flashback_query_clause of within the subquery to update table with past data. Please refer to the flashback_query_clause of SELECT for more information on this clause.

expr

Specify an expression that resolves to the new value assigned to the corresponding column.

DEFAULT

Specify DEFAULT to set the column to the value previously specified as the default value for the column. If no default value for the corresponding column has been specified, then the database sets the column to null.

Restriction on Updating to Default Values

You cannot specify DEFAULT if you are updating a view.

VALUE Clause

The VALUE clause lets you specify the entire row of an object table.

Restriction on the VALUE clause

You can specify this clause only for an object table.

where_clause

The where_clause lets you restrict the rows updated to those for which the specified condition is true. If you omit this clause, then the database updates all rows in the table or view. Please refer to Chapter 6, " Conditions" for the syntax of condition.

The where_clause determines the rows in which values are updated. If you do not specify the where_clause, then all rows are updated. For each row that satisfies the where_clause, the columns to the left of the equality operator (=) in the update_set_clause are set to the values of the corresponding expressions to the right of the operator. The expressions are evaluated as the row is updated.

returning_clause

The returning clause retrieves the rows affected by a DML statement. You can specify this clause for tables and materialized views and for views with a single base table.

When operating on a single row, a DML statement with a returning_clause can retrieve column expressions using the affected row, rowid, and REFs to the affected row and store them in host variables or PL/SQL variables.

When operating on multiple rows, a DML statement with the returning_clause stores values from expressions, rowids, and REFs involving the affected rows in bind arrays.

expr

Each item in the expr list must be a valid expression syntax.

INTO

The INTO clause indicates that the values of the changed rows are to be stored in the variable(s) specified in data_item list.

data_item

Each data_item is a host variable or PL/SQL variable that stores the retrieved expr value.

For each expression in the RETURNING list, you must specify a corresponding type-compatible PL/SQL variable or host variable in the INTO list.

Restrictions

The following restrictions apply to the RETURNING clause:

• The expr is restricted as follows:

  • Each expr must be a simple expression or a single-set aggregate function expression. You cannot combine simple expressions and single-set aggregate function expressions in the same returning_clause.

  • Single-set aggregate function expressions cannot include the DISTINCT keyword.

• You cannot specify the returning_clause for a multitable insert.

• You cannot use this clause with parallel DML or with remote objects.

• You cannot retrieve LONG types with this clause.

• You cannot specify this clause for a view on which an INSTEAD OF trigger has been defined.

Examples

Updating a Table: Examples

The following statement gives null commissions to all employees with the job SH_CLERK:

UPDATE employees
   SET commission_pct = NULL
   WHERE job_id = 'SH_CLERK';

The following statement promotes Douglas Grant to manager of Department 20 with a $1,000 raise:

UPDATE employees SET 
    job_id = 'SA_MAN', salary = salary + 1000, department_id = 120 
    WHERE first_name||' '||last_name = 'Douglas Grant'; 

The following statement increases the salary of an employee in the employees table on the remote database:

UPDATE employees@remote
   SET salary = salary*1.1
   WHERE last_name = 'Baer';

The next example shows the following syntactic constructs of the UPDATE statement:

• Both forms of the update_set_clause together in a single statement

• A correlated subquery

• A where_clause to limit the updated rows

UPDATE employees a 
    SET department_id = 
        (SELECT department_id 
            FROM departments 
            WHERE location_id = '2100'), 
        (salary, commission_pct) = 
        (SELECT 1.1*AVG(salary), 1.5*AVG(commission_pct) 
          FROM employees b 
          WHERE a.department_id = b.department_id) 
    WHERE department_id IN 
        (SELECT department_id 
          FROM departments
          WHERE location_id = 2900 
              OR location_id = 2700); 

The preceding UPDATE statement performs the following operations:

• Updates only those employees who work in Geneva or Munich (locations 2900 and 2700)

• Sets department_id for these employees to the department_id corresponding to Bombay (location_id 2100)

• Sets each employee's salary to 1.1 times the average salary of their department

• Sets each employee's commission to 1.5 times the average commission of their department

Updating a Partition: Example

The following example updates values in a single partition of the sales table:

UPDATE sales PARTITION (sales_q1_1999) s
   SET s.promo_id = 494
   WHERE amount_sold > 9000;

Updating an Object Table: Example

The following statement updates a row of object table table1 by selecting a row from another object table table2:

UPDATE table1 p SET VALUE(p) =
   (SELECT VALUE(q) FROM table2 q WHERE p.id = q.id)
   WHERE p.id = 10;

The example uses the VALUE object reference function in both the SET clause and the subquery.

Correlated Update: Example

The following example updates particular rows of the projs nested table corresponding to the department whose department number equals 123:

UPDATE TABLE(SELECT projs 
           FROM dept d WHERE d.dno = 123)  p 
  SET p.budgets = p.budgets + 1 
  WHERE p.pno IN (123, 456);

Using the RETURNING Clause During UPDATE: Example

The following example returns values from the updated row and stores the result in PL/SQL variables bnd1, bnd2, bnd3:

UPDATE employees
  SET job_id ='SA_MAN', salary = salary + 1000, department_id = 140
  WHERE last_name = 'Jones'
  RETURNING salary*0.25, last_name, department_id
    INTO :bnd1, :bnd2, :bnd3;

The following example shows that you can specify a single-set aggregate function in the expression of the returning clause:

UPDATE employees
   SET salary = salary * 1.1
   WHERE department_id = 100
   RETURNING SUM(salary) INTO :bnd1;