mysql - 在 mysql 中连接结果值

Question

我可以连接结果值，然后将最终值作为输出发送吗？

WHILE(LENGTH(totalexpenseamount )>0) DO
        BEGIN
              SET totalshipmentexpenseamount = CONCAT(totalshipmentexpenseamount,',',indshipmentexpenseamount);
END;
    END WHILE;

但最后 totalshipmentexpenseamount 没有任何值(value)。

Answer 1

不知道您提供的代码之前是什么，但您可以尝试以下操作:

WHILE(LENGTH(totalexpenseamount )>0) DO
        BEGIN
              SET totalshipmentexpenseamount = CONCAT(COALESCE(totalshipmentexpenseamount, ''),',',indshipmentexpenseamount);
END;
    END WHILE;

这是因为 totalshipmentexpenseamount 第一次设置为 null 并且当你将 null 与其他东西连接时它会出现 空。如果 totalshipmentexpenseamount 为 null

， coalesce 将返回空

编辑:

改成这个

WHILE(LENGTH(totalexpenseamount )>0) DO
BEGIN
    SET totalshipmentexpenseamount = COALESCE(CONCAT(totalshipmentexpenseamount,',',indshipmentexpenseamount), indshipmentexpenseamount);
END;
WHILE;

由于您使用逗号连接，这将在第一次传递时设置 indshipmentexpenseamount 的值，否则将使用逗号连接 totalshipmentexpenseamount 和 indshipmentexpenseamount