检查游标是否返回任何内容

Question

如何在mysql的过程函数中检查游标是否返回任何内容？

是否可以避免执行IF (SELECT COUNT(*) FROM stock ...而是以某种方式检查_cur变量？

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

向游标添加继续处理程序。请参阅MySQL文档中的exanples。

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