21.8.15.1. Why `mysql_store_result()` Sometimes Returns `NULL` After`mysql_query()` Returns Success

It is possible for mysql_store_result() to return NULL following a successful call to mysql_query(). When this happens, it means one of the following conditions occurred:

There was a malloc() failure (for example, if the result set was too large).
The data could not be read (an error occurred on the connection).
The query returned no data (for example, it was an INSERT, UPDATE, or DELETE).

You can always check whether the statement should have produced a nonempty result by calling mysql_field_count(). If mysql_field_count() returns zero, the result is empty and the last query was a statement that does not return values (for example, an INSERT or a DELETE). If mysql_field_count() returns a nonzero value, the statement should have produced a nonempty result. See the description of the mysql_field_count() function for an example.

You can test for an error by calling mysql_error() or mysql_errno().

21.8.15.1. Why mysql_store_result() Sometimes Returns NULL Aftermysql_query() Returns Success

21.8.15.1. Why `mysql_store_result()` Sometimes Returns `NULL` After`mysql_query()` Returns Success