Question

我正在尝试以下条件：如果Loans表中的任何贷款具有OutstandingAmount＆lt; 0，删除数据库中的所有相关信息。我必须在一个命令中完成它，因此，我尝试使用INNER JOIN：

DELETE A, B, C, D, E
FROM Loans AS T1
INNER JOIN Payments T2 ON T1.LoanID = T2.LoanID
INNER JOIN Repayments T3 ON T1.LoanID = T3.LoanID
INNER JOIN Histories T4 ON T1.LoanID = T4.LoanID
INNER JOIN LoanRequests T5 ON T1.RequestDate = T5.RequestDate AND T1.BID = T5.BID
INNER JOIN Commits T6 ON T1.RequestDate = T6.requestDate AND T1.BID = T6.BID
WHERE T1.OutstandingAmount < 0

但是，这个命令在“DELETE A，B”中给出了语法错误，我甚至不确定这是否有效。任何帮助将不胜感激。谢谢。

Answer 1

正如Gordon Linoff在评论中写道，你只能从每个删除声明中的一个表中删除。

你基本上有两个选择：

在外键中使用删除级联（这可能是最好的事情要做）
对每个表使用delete语句，但将整个删除过程包装在事务中。

将删除级联添加到外键意味着删除并重新创建它们：

ALTER TABLE dbo.Loans
DROP CONSTRAINT FK_Loans_Payments; 

ALTER TABLE dbo.Loans
ADD CONSTRAINT FK_Loans_Payments FOREIGN KEY (LoanID) REFERENCES Payments(LoanID) ON DELETE CASCADE;

使用事务来包装单个删除语句：

BEGIN TRASACTION

BEGIN TRY

DELETE c
FROM Commits 
INNER JOIN Loans l ON l.RequestDate = c.RequestDate 
WHERE l.OutstandingAmount < 0

DELETE lr
FROM LoanRequests lr
INNER JOIN Loans l ON l.RequestDate = lr.RequestDate 
WHERE l.OutstandingAmount < 0

-- more of the same...

DELETE 
FROM Loans
WHERE OutstandingAmount < 0

COMMIT TRANSACTION

END TRY
BEGIN CATCH

    IF @@TRANCOUNT > 0
        ROLLBACK TRANSACTION
END CATCH

在DELETE中使用INNER JOIN

1 个答案: