B Supported SQL Syntax and Functions

The following topics describe supported SQL Syntax and 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 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
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 ()

LEN ()

LENGTHB ()

DATALENGTH ()

LENGTHC ()

LEN ()

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
    

    Note:

    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.