B Supported SQL Syntax and Functions

This appendix contains the following sections:

Supported SQL Statements
Oracle Functions

B.1 Supported SQL Statements

Oracle Database Gateway for ODBC supports the following statements, but only if the ODBC driver and non-Oracle system can execute them and if the statements contain supported Oracle SQL functions:

DELETE
INSERT
SELECT
UPDATE

With a few exceptions, the gateway provides full support for Oracle DELETE, INSERT, SELECT, and UPDATE statements.

The gateway does not support Oracle data definition language (DDL) statements. No form of the Oracle ALTER, CREATE, DROP, GRANT, or TRUNCATE statements can be used. Instead, for ALTER, CREATE, DROP, and GRANT statements, use the pass-through feature of the gateway if you need to use DDL statements against the non-Oracle system database.

Note:

TRUNCATE cannot be used in a pass-through statement.

B.1.1 DELETE

The DELETE statement is fully supported. However, only Oracle functions supported by the non-Oracle system can be used.

B.1.2 INSERT

The INSERT statement is fully supported. However, only Oracle functions supported by the non-Oracle system can be used.

B.1.3 SELECT

The SELECT statement is fully supported, with these exceptions:

CONNECT BY condition
NOWAIT
START WITH condition
WHERE CURRENT OF

B.1.4 UPDATE

The UPDATE statement is fully supported. However, only Oracle functions supported by the non-Oracle system can be used. Also, you cannot have SQL statements in the subquery that refer to the same table name in the outer query. Subqueries are not supported in the SET clause.

B.2 Oracle Functions

All functions are evaluated by the non-Oracle system after the gateway has converted them to the native SQL. Only a limited set of functions are assumed to be supported by the non-Oracle system. Most Oracle functions have no equivalent function in this limited set. Consequently, although post-processing is performed by the Oracle database, many Oracle functions are not supported by Oracle Database Gateway for ODBC, possibly impacting performance.

If an Oracle SQL function is not supported by Oracle Database Gateway for ODBC, this function is not supported in DELETE, INSERT, or UPDATE statements. In SELECT statements, these functions are evaluated by the Oracle database and processed after they are returned from the non-Oracle system.

If an unsupported function is used in a DELETE, INSERT, or UPDATE statement, it generates the following Oracle error:

ORA-02070: database db_link_name does not support function in this context

Oracle Database Gateway for ODBC assumes that the following minimum set of SQL functions is supported by the ODBC driver provider that is being used:

AVG(exp)
LIKE(exp)
COUNT(*)
MAX(exp)
MIN(exp)
NOT