unsigned intmysql_num_fields(MYSQL_RES *result) To pass aMYSQL* argument instead, useunsigned int mysql_field_count(MYSQL *mysql).
Returns the number of columns in a result set.
You can get the number of columns either from a pointer to a result set or to a connection handler. You would use the connection handler ifmysql_store_result() ormysql_use_result() returnedNULL (and thus you have no result set pointer). In this case, you can callmysql_field_count() to determine whethermysql_store_result() should have produced a nonempty result. This enables the client program to take proper action without knowing whether the query was aSELECT (orSELECT-like) statement. The example shown here illustrates how this may be done.
SeeSection 3.6.9, “NULL mysql_store_result() Return After mysql_query() Success”.
MYSQL_RES *result;unsigned int num_fields;unsigned int num_rows;if (mysql_query(&mysql,query_string)){ // error}else // query succeeded, process any data returned by it{ result = mysql_store_result(&mysql); if (result) // there are rows { num_fields = mysql_num_fields(result); // retrieve rows, then call mysql_free_result(result) } else // mysql_store_result() returned nothing; should it have? { if (mysql_errno(&mysql)) { fprintf(stderr, "Error: %s\n", mysql_error(&mysql)); } else if (mysql_field_count(&mysql) == 0) { // query does not return data // (it was not a SELECT) num_rows = mysql_affected_rows(&mysql); } }} An alternative (if you know that your query should have returned a result set) is to replace themysql_errno(&mysql) call with a check whethermysql_field_count(&mysql) returns 0. This happens only if something went wrong.