sql - SQL - 删除和子查询

Question

以下是我编写的一个 sql 查询，用于删除放置表中的所有记录，其中placement.op_number= 返回记录的列表。

子查询单独工作正常，只返回OP_NUMBER列（两行）。

我得到的错误是：

子查询最多可以返回一条记录

DELETE
FROM PLACEMENT
WHERE PLACEMENT.OP_NUMBER = (SELECT OP_NUMBER
                             FROM Opening
                             WHERE opening.qual_code = "SEC-45");

我究竟做错了什么？

Answer 1

使用IN而不是等于：

delete
from PLACEMENT
where PLACEMENT.OP_NUMBER in (
        select OP_NUMBER
        from Opening
        where opening.qual_code = "SEC-45"
        );

Answer 2

DELETE
FROM PLACEMENT
WHERE EXISTS (SELECT OP_NUMBER FROM Opening
               WHERE opening.qual_code = "SEC-45" 
              AND OP_NUMBER = PLACEMENT.OP_NUMBER);

Answer 3

当前，您正在将 PLACEMENT.OP_NUMBER 与记录集进行比较 - Int 与记录集。您将需要使用 IN 关键字来将条件与多个值进行比较

您的新查询应如下所示 -

DELETE
FROM PLACEMENT
WHERE PLACEMENT.OP_NUMBER IN (SELECT OP_NUMBER
                             FROM Opening
                             WHERE opening.qual_code = "SEC-45");