Oracle Transparent Gateway for Informix Administrator's Guide
Release 8.1.6

A80981-01

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Supported SQL Syntax and Functions

This appendix contains the following sections:.

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 Informix database.

See Also:

"Using the Pass-Through Feature" and Oracle8i SQL Reference for a detailed descriptions of keywords, parameters, and options. 

DELETE

The DELETE statement is fully supported. However, only Oracle functions supported by Informix can be used. Also, you cannot have SQL statements in the subquery that refer to the same table name in the outer query.

See Also:

"Functions Supported by Informix" for a list of supported functions. 

INSERT

The INSERT statement is fully supported. However, only Oracle functions supported by Informix can be used. Also, you cannot have SQL statements in the subquery that refer to the same table name in the outer query.

See Also:

"Functions Supported by Informix" for a list of supported functions. 

SELECT

The SELECT statement is fully supported, with these exceptions:

UPDATE

The UPDATE statement is fully supported. However, only Oracle functions supported by Informix 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. Informix does not support table aliases in UPDATE.

See Also:

"Functions Supported by Informix" for a list of supported functions. 

Oracle Functions

All functions are evaluated by the Informix database after the gateway has converted them to Informix SQL.

Functions Not Supported by Informix

Oracle SQL functions with no equivalent function in Informix are not supported in DELETE, INSERT, or UPDATE statements, but are evaluated by the Oracle database server if the statement is a SELECT statement. That is, the Oracle database server 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 Informix

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

Arithmetic Operators

Oracle  Informix 

Comparison Operators

Oracle  Informix 

>= 

>= 

<= 

<= 

<>, !=, ^= 

<> 

IS NULL 

IS NULL 

IS NOT NULL 

IS NOT NULL 

String Functions

Oracle  Informix 

||, CONCAT 

|| 

ASCII 

ASCII 

CHR 

CHR 

LENGTH 

LENGTH 

Group Functions

Oracle  Informix 

AVG 

AVG 

COUNT 

COUNT 

MAX 

MAX 

MIN 

MIN 

SUM 

SUM 

Pattern Matches

Oracle  Informix 

LIKE 'a%' 

LIKE "a%" 

LIKE 'a_' 

LIKE "a_" 

LIKE 'a\%' ESCAPE '\' 

LIKE "a\%" ESCAPE "\" 

NOT LIKE 

NOT LIKE 

Date Functions

Oracle  Informix 

date + number 

date + number 

date - number 

date - number 

date + date 

date + date 

date - date 

date - date 

Other Functions

Oracle  Informix 

ABS 

ABS 

COS 

COS 

EXP 

EXP 

LOG10 

LOG10 

LN 

LOGN 

LTRIM(char

TRIM(LEADING FROM char

MOD 

MOD 

POWER (m,n

POW(m,n

RTRIM(char

TRIM(TRAILING FROM char

ROUND (with 1 argument) 

ROUND 

SIN 

SIN 

SQRT 

SQRT 

TAN 

TAN 

TRUNC (with 1 argument) 

TRUNC 

Functions Supported by the Gateway

If the Oracle function has no equivalent function in Informix, 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 one function even though there is no equivalent in Informix. This function is the TO_DATE function:

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, yyyy-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.


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