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Oracle® Database Gateway for Informix User's Guide
11g Release 1 (11.1)

B31047-03
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B Supported SQL Syntax and Functions

This appendix contains the following sections:

B.1 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:

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

B.1.1 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.

B.1.2 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.

B.1.3 SELECT

The SELECT statement is fully supported, with these exceptions:

  • CONNECT BY condition

  • NOWAIT

  • START WITH condition

  • Subquery in HAVING clause

B.1.4 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.

B.2 Oracle Functions

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

B.2.1 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 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

B.2.2 Functions Supported by Informix

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

B.2.2.1 Arithmetic Operators

Oracle Informix
+ +
- -
* *
/ /

B.2.2.2 Comparison Operators

Oracle Informix
= =
> >
< <
>= >=
<= <=
<>, !=, ^= <>
IS NOT NULL IS NOT NULL
IS NULL IS NULL

B.2.2.3 Group Functions

Oracle Informix
AVG AVG
COUNT COUNT
MAX MAX
MIN MIN
SUM SUM

B.2.2.4 String Functions

Oracle Informix
||, CONCAT ||
ASCII ASCII
CHR CHR
LENGTH LENGTH

B.2.2.5 Pattern Matches

Oracle Informix
LIKE 'a%' LIKE "a%"
LIKE 'a_' LIKE "a_"
LIKE 'a\%' ESCAPE '\' LIKE "a\%" ESCAPE "\"
NOT LIKE NOT LIKE

B.2.2.6 Date Functions

Oracle Informix
date + number date + number
date - number date - number
date + date date + date
date - date date - date

B.2.2.7 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

B.2.3 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.