通過連接多列刪除查詢

Question

我有表T1，列C1，C2和表T2，列C3，C4，C5。我想從T1中刪除記錄，其中C1 = C3 AND C2 = C4和C5 ='123'。什麼將是我試過以下查詢

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

但這是行不通的。

Answer 1

SQL Server中沒有WHERE (x,y) = (a,b)語法，很抱歉。這是你如何執行刪除，基於連接，無論多少列參與加入：

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

Answer 2

SQL Server支持一個額外的FROM子句DELETE語句。

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

Answer 3

可以使用exists做到這一點：

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

一般情況下，使用exists比使用in使用子查詢，因爲空白可導致後者做奇怪的方式行爲更好。