檢查遊標是否返回任何東西

Question

如何在mysql中的過程函數中檢查遊標是否返回任何東西？

是否有可能避免做IF (SELECT COUNT(*) FROM stock ...，而是以某種方式檢查_cur變量？

程序功能

DELIMITER $$ 

DROP FUNCTION IF EXISTS `stock_first_available_id` $$ 
CREATE DEFINER=`dynaccount`@`localhost` FUNCTION `stock_first_available_id`(_running_total_limit INT, _product_id INT, _group_id INT) RETURNS INT 
BEGIN 
    DECLARE _running_count INT default 0; 
    DECLARE _id INT; 
    DECLARE _current_id INT; 
    DECLARE _sum_count INT; 
    DECLARE _cur CURSOR FOR SELECT id, count FROM stock WHERE group_id=_group_id && type=2 && product_id=_product_id ORDER BY time DESC, id DESC; 

    IF (SELECT COUNT(*) FROM stock WHERE group_id=_group_id && type=2 && product_id=_product_id) = 0 THEN 
     RETURN 0; 
    END IF; 

    OPEN _cur; 

    read_loop: LOOP 
     FETCH _cur INTO _id, _sum_count; 

     SET _running_count = _running_count + _sum_count; 
     SET _current_id = _id; 

     IF _running_count > _running_total_limit THEN 
      LEAVE read_loop; 
     END IF; 
    END LOOP read_loop; 

    CLOSE _cur; 

    RETURN _current_id; 
END $$ 

DELIMITER ; 

Answer 1

添加繼續處理程序光標。請參閱MySQL文檔中的exanples。

http://dev.mysql.com/doc/refman/5.0/en/cursors.html