9.1.3.52 mysql_store_result()

MYSQL_RES *mysql_store_result(MYSQL *mysql)

Description

You must call mysql_store_result() or mysql_use_result() for every query that successfully retrieves data (SELECT, SHOW, DESCRIBE, EXPLAIN).

You don't have to call mysql_store_result() or mysql_use_result() for other queries, but it will not do any harm or cause any notable performance if you call mysql_store_result() in all cases. You can detect if the query didn't have a result set by checking if mysql_store_result() returns 0 (more about this later one).

If you want to know if the query should return a result set or not, you can use mysql_field_count() to check for this. See section 9.1.3.20 mysql_field_count().

mysql_store_result() reads the entire result of a query to the client, allocates a MYSQL_RES structure, and places the result into this structure.

mysql_store_result() returns a null pointer if the query didn't return a result set (if the query was, for example, an INSERT statement).

mysql_store_result() also returns a null pointer if reading of the result set failed. You can check if you got an error by checking if mysql_error() doesn't return a null pointer, if mysql_errno() returns <> 0, or if mysql_field_count() returns <> 0.

An empty result set is returned if there are no rows returned. (An empty result set differs from a null pointer as a return value.)

Once you have called mysql_store_result() and got a result back that isn't a null pointer, you may call mysql_num_rows() to find out how many rows are in the result set.

You can call mysql_fetch_row() to fetch rows from the result set, or mysql_row_seek() and mysql_row_tell() to obtain or set the current row position within the result set.

You must call mysql_free_result() once you are done with the result set.

See section 9.1.12.1 Why Is It that After mysql_query() Returns Success, mysql_store_result() Sometimes Returns NULL?.

Return Values

A MYSQL_RES result structure with the results. NULL if an error occurred.

Errors

CR_COMMANDS_OUT_OF_SYNC

Commands were executed in an improper order.

CR_OUT_OF_MEMORY

Out of memory.

CR_SERVER_GONE_ERROR

The MySQL server has gone away.

CR_SERVER_LOST

The connection to the server was lost during the query.

CR_UNKNOWN_ERROR

An unknown error occurred.

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