Question

我的SQL：

CREATE PROCEDURE INV_MIN_PURCHASE_PRICE()
BEGIN
DECLARE done INT;
DECLARE current_inventory_ID INT;
DECLARE cur1 CURSOR FOR SELECT inventory_ID FROM _inventory;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

SET done = 0;
OPEN cur1;

REPEAT

    FETCH cur1 INTO current_inventory_ID;
    UPDATE _debug SET rows=rows+1;

UNTIL done
END REPEAT;

CLOSE cur1;

END;

当我调用此过程时，MySQL只获取一行（_debug rows增加1）。为什么？？这是一个错误吗？

Answer 1

我在MySQL中遇到了与存储过程相同的问题。它应该从表中获取某个列中具有空值的所有记录，然后从另一个表中填充该值。然而，它在一条记录后停止了：

CREATE PROCEDURE `updateRecord`()
    BEGIN

    DECLARE done INT DEFAULT FALSE;
    DECLARE recordId, newValue INT;
    DECLARE current_record CURSOR FOR SELECT id FROM A where b_id is null;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE; 

    OPEN current_record;

    main_loop: LOOP
        FETCH current_record INTO recordId;

        IF done THEN
             LEAVE main_loop;
        END IF;

        -- fetching some value from table b
        select id into newValue from B where ...

       -- setting new value in record
       update A set b_id = newValue where id = recordId;    

      END LOOP;
    END

答案是，如果游标没有返回任何行，而且如果表B上的select没有返回任何行，则不仅执行“找不到处理程序”。我的解决方案是使用由处理程序设置的第二个变量，并在select：

之后重置“done”变量

    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE, noBfound = TRUE;    

           [...]

           select id into newValue from B where ...

           IF (noBfound = TRUE) THEN 
               SET done = FALSE;
           END IF;

           [...]

补充：显然可以在没有第二个变量的情况下通过简单地重置选择后的“完成”：

    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE; 

           [...]

           select id into newValue from B where ...

           SET done = FALSE;

           [...]

Answer 2

您是否尝试过LOOP而不是REPEAT构造？似乎在MySQL中工作得更好。用以下代码将REPEAT替换为END REPEAT部分：

inv_loop: LOOP
    FETCH cur1 INTO current_inventory_ID;
    IF done = 1 THEN
        LEAVE inv_loop;
    END IF;
    UPDATE _debug SET rows=rows+1;
END LOOP;

Answer 3

IF done THEN
         LEAVE main_loop;
ELSE
         ITERATE main_loop;
END IF;

MySQL Cursor只获取一行

3 个答案: