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(mysql.info)mysql_num_fields

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`mysql_num_fields()'
....................

`unsigned int mysql_num_fields(MYSQL_RES *result)'

or

`unsigned int mysql_num_fields(MYSQL *mysql)'

The second form doesn't work on MySQL Version 3.22.24 or newer.  To
pass a `MYSQL*' argument, you must use `unsigned int
mysql_field_count(MYSQL *mysql)' instead.

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 or not
`mysql_store_result()' should have produced a non-empty result.  This
allows the client program to take proper action without knowing whether
or not the query was a `SELECT' (or `SELECT'-like) statement.  The
example shown below illustrates how this may be done.

Note: `NULL mysql_store_result()'.

Return Values
.............

An unsigned integer representing the number of fields 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 if
`mysql_field_count(&mysql)' is = 0.  This will only happen if something
went wrong.