通过连接多个列来删除查询

Question

我有表T1，列C1，C2和表T2，列C3，C4，C5。我想删除T1中的记录，其中C1 = C3和C2 = C4，C5 ='123'。我试过的查询是什么

DELETE FROM T1 WHERE (C1,C2) = SELECT (C3,C4) FROM T2 WHERE C5 = '123'

但这不起作用。

Answer 1

SQL Server中没有WHERE (x,y) = (a,b)语法，抱歉。这是基于连接执行删除的方式，无论连接中涉及多少列：

DELETE t1 
  FROM t1
  INNER JOIN t2
  ON t1.c1 = t2.c3
  AND t1.c2 = t2.c4
  WHERE t2.c5 = '123';

Answer 2

您可以使用exists：

执行此操作

DELETE FROM T1
    WHERE exists (SELECT 1 FROM T2 WHERE C5 = '123' and t2.c3 = t1.c1 and t2.c4 = t1.c2) )

通常，使用exists比使用带有子查询的in更好，因为NULL会导致后者以奇怪的方式执行行为。

Answer 3

SQL Server在DELETE语句中支持额外的FROM子句。

DELETE FROM T1
FROM T1
INNER JOIN T2
  ON T1.c1 = T2.c3
  AND T1.c2 = T2.c4
  WHERE c5 = '123';