B Supported SQL Syntax and Functions

This appendix contains the following sections:

Supported SQL Statements
Oracle Functions

Supported SQL Statements

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, use the pass-through feature of the gateway if you need to use DDL statements against the SQL Server database.

Note:

TRUNCATE cannot be used in a pass-through statement.

See Also:

Oracle Database Reference for a detailed descriptions of keywords, parameters, and options.

DELETE

The DELETE statement is fully supported. However, only Oracle functions supported by SQL Server can be used.

See Also:

"Functions Supported by SQL Server" for a list of supported functions.

INSERT

The INSERT statement is fully supported. However, only Oracle functions supported by SQL Server can be used.

See Also:

"Functions Supported by SQL Server" for a list of supported functions.

SELECT

The SELECT statement is fully supported, with these exceptions:

CONNECT BY condition
NOWAIT
START WITH condition
WHERE CURRENT OF

UPDATE

The UPDATE statement is fully supported. However, only Oracle functions supported by SQL Server can be used.

See Also:

"Functions Supported by SQL Server" for a list of supported functions.

Oracle Functions

All functions are evaluated by the SQL Server database after the gateway has converted them to SQL Server SQL equivalents. The exception is the TO_DATE function, which is evaluated by the gateway.

Functions Not Supported by SQL Server

Oracle SQL functions with no equivalent function in SQL Server are not supported in DELETE, INSERT, or UPDATE statements, but are evaluated by the Oracle database if the statement is a SELECT statement. That is, the Oracle database performs post-processing of SELECT statements sent to the gateway.

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

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

Functions Supported by SQL Server

The gateway translates the following Oracle database functions in SQL statements to their equivalent SQL Server functions:

Arithmetic Operators
Comparison Operators
Pattern Matching
Group Functions
String Functions
Other Functions

Arithmetic Operators

Oracle	SQL Server
`+`	`+`
`-`	`-`
`*`	`*`
`/`	`/`

Comparison Operators

Oracle	SQL Server
`=`	`=`
`>`	`>`
`<`	`<`
`>=`	`>=`
`<=`	`<=`
`<>, !=, ^=`	`<>`
`IS NOT NULL`	`IS NOT NULL`
`IS NULL`	`IS NULL`

Pattern Matching

Oracle	SQL Server
`LIKE`	`LIKE`
`NOT LIKE`	`NOT LIKE`

Group Functions

Oracle	SQL Server
`AVG`	`AVG`
`COUNT`	`COUNT`
`MAX`	`MAX`
`MIN`	`MIN`
`SUM`	`SUM`

String Functions

Oracle	SQL Server
`\|\|, CONCAT`	`+` `(expression1` `+` `expression2)`
`ASCII`	`ASCII`
`CHR`	`CHAR`
`INSTR` (with two arguments)	`CHARINDEX`
`LENGTH`	`DATALENGTH`
`LOWER`	`LOWER`
`LTRIM`	`LTRIM`
`RTRIM`	`RTRIM`
`SUBSTR` (second argument cannot be a negative number)	`SUBSTRING`
`UPPER`	`UPPER`

Other Functions

Oracle	SQL Server
`ABS`	`ABS`
`CEIL`	`CEILING`
`COS`	`COS`
`EXP`	`EXP`
`FLOOR`	`FLOOR`
`LN`	`LOG`
`LOG`	`LOG10`
`MOD`	`%`
`NOT NVL`	`IS NOT NULL`
`NVL`	`IS NULL`
`POWER`	`POWER`
`ROUND`	`ROUND`
`SIN`	`SIN`
`SQRT`	`SQRT`
`TAN`	`TAN`

Functions Supported by the Gateway

If an Oracle function has no equivalent function in SQL Server, the Oracle function is not translated into the SQL statement and must be post-processed if the SQL statement is a SELECT.

The gateway, however, does support the TO_DATE function equivalent in SQL Server, as follows:

TO_DATE(date_string | date_column)

Where:

date_string is converted to a string with the following format:

yyyy-mm-dd hh:mi:ss.fff

Recommendation:

Supply the date string with the same format as the result (that is, yyyyy-mm-dd hh:mi:ss.fff).

date_column is a column with a date data type. It is converted to a parameter with a timestamp data type.