This appendix contains the following sections:
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 detailed descriptions of keywords, parameters, and options.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.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.The SELECT statement is fully supported, with these exceptions:
CONNECT BY condition
NOWAIT
START WITH condition
Subquery in HAVING clause
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.All functions are evaluated by the Informix database after the gateway has converted them to Informix SQL.
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
The gateway translates the following Oracle database functions in SQL statements to their equivalent Informix functions:
| Oracle | Informix |
|---|---|
= |
= |
> |
> |
< |
< |
>= |
>= |
<= |
<= |
<>, !=, ^= |
<> |
IS NOT NULL |
IS NOT NULL |
IS NULL |
IS NULL |
| Oracle | Informix |
|---|---|
LIKE 'a%' |
LIKE "a%" |
LIKE 'a_' |
LIKE "a_" |
LIKE 'a\%' ESCAPE '\' |
LIKE "a\%" ESCAPE "\" |
NOT LIKE |
NOT LIKE |
| Oracle | Informix |
|---|---|
date + number |
date + number |
date - number |
date - number |
date + date |
date + date |
date - date |
date - date |
| 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 |
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.