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(mysql.info.gz) mysql_field_count

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 22.2.3.20 `mysql_field_count()'
 ...............................
 
 `unsigned int mysql_field_count(MYSQL *mysql)'
 
 If you are using a version of MySQL earlier than Version 3.22.24, you
 should use `unsigned int mysql_num_fields(MYSQL *mysql)' instead.
 
 Description
 ...........
 
 Returns the number of columns for the most recent query on the
 connection.
 
 The normal use of this function is when `mysql_store_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 non-empty result.  This
 allows 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.
 
  `NULL mysql_store_result()' NULL mysql_store_result.
 
 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_field_count(&mysql) == 0)
              {
                  // query does not return data
                  // (it was not a SELECT)
                  num_rows = mysql_affected_rows(&mysql);
              }
              else // mysql_store_result() should have returned data
              {
                  fprintf(stderr, "Error: %s\n", mysql_error(&mysql));
              }
          }
      }
 
 An alternative is to replace the `mysql_field_count(&mysql)' call with
 `mysql_errno(&mysql)'.  In this case, you are checking directly for an
 error from `mysql_store_result()' rather than inferring from the value
 of `mysql_field_count()' whether the statement was a `SELECT'.
 
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