unsigned int mysql_num_fields(MYSQL_RES *result)

To pass a MYSQL* argument instead, use unsigned int mysql_field_count(MYSQL *mysql).

Description

Returns the number of columns in a result set.

Note that you can get the number of columns either from a pointer to a result set or to a connection handle. You would use the connection handle if mysql_store_result() or mysql_use_result() returned NULL (and thus you have no result set pointer). In this case, you can call mysql_field_count() to determine whether mysql_store_result() should have produced a nonempty result. This enables the client program to take proper action without knowing whether the query was a SELECT (or SELECT-like) statement. The example shown here illustrates how this may be done.

See Section 22.8.15.1, "Why mysql_store_result() Sometimes Returns NULL After mysql_query() Returns Success".

Return Values

An unsigned integer representing the number of columns in a result set.

Errors

None.

Example

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 the mysql_errno(&mysql) call with a check whether mysql_field_count(&mysql) returns 0. This happens only if something went wrong.