25.2.13.1. 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 couldn't 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 non-empty 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 non-zero
value, the statement should have produced a non-empty 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().
