Question

我有2个表tlbinvoice和tblRel_Inv_Course，其中InvoiceID是外键。当我尝试从Invoice表中删除一行时，出现错误

无法删除外键约束

下面是两个查询和数据：

 select * from  invoice where InvoiceID=19

    InvoiceID   invimagetype  location
    -----------------------------------
    19          image/jpeg    network


 select * from  Rel_Inv_Course where CourseID=4262 

    Rel_I_C_ID  CourseID    InvoiceID
    ----------------------------------
    2255        4262            19

我尝试过的：

delete from [TAP].[dbo].Invoice 
where InvoiceID = (select InvoiceID 
                   from Rel_Inv_Course 
                   where CourseID = 4262)

delete from Rel_Inv_Course 
where CourseID = 4262

但是我不能这样做。我需要从发票编号为19的表的两行中删除。请帮助。

Answer 1

正如评论所说，您所需要做的就是翻转delete语句，您应该会很好：

您可以考虑将它们包装在begin tran中，以便您检查删除是否也删除了您想要的数据：

  Begin Tran
    DECLARE @INVOICEID INT
    SET @INVOICE = (select InvoiceID from Rel_Inv_Course where CourseID=4262)

        delete from Rel_Inv_Course where CourseID=4262

        delete from [TAP].[dbo].Invoice where InvoiceID =(@INVOICEID)

    --Select * from Rel_Inv_Course 
    --Select * from [dbo].Invoice 

    --If satisfied with deletes finally commit tran
    --If not satisfied --> Rollback Tran
    Commit Tran

Answer 2

使用一些示例数据和DDL可能更易于解释：

(?<=_)\d\.\d

您会注意到USE Sandbox; GO CREATE TABLE dbo.Parent (ID int NOT NULL, SomeString varchar(100) NOT NULL); GO CREATE TABLE dbo.Child (ID int NOT NULL, ParentID int NOT NULL, AnotherString varchar(100) NOT NULL); GO ALTER TABLE dbo.Parent ADD CONSTRAINT PK_PID PRIMARY KEY CLUSTERED (ID); ALTER TABLE dbo.Child ADD CONSTRAINT PK_CID PRIMARY KEY CLUSTERED (ID); ALTER TABLE dbo.Child ADD CONSTRAINT FK_PID FOREIGN KEY (ParentID) REFERENCES dbo.Parent (ID); GO INSERT INTO dbo.Parent (ID, SomeString) VALUES (1, 'sdfkgjbhasdfg'), (2, 'sdfkjsdbhkf'); GO INSERT INTO dbo.Child (ID, ParentID, AnotherString) VALUES (1, 1, 'asdfkiashjbd'), (2, 1, '#asldjasbhdk,'), (3, 2, 'asfjasdfj'); GO --Try to delete a row in Parent: DELETE FROM dbo.Parent WHERE ID = 2; --No surprise it failed GO --Try to delete a row in child DELETE FROM dbo.Child WHERE ID = 2; --This worked fine. GO -- --If we check, however, ParentID 1 and 2 are still in the table: SELECT * FROM dbo.Child; --We want to delete ID 1 in parent, so we need to delete the other row DELETE FROM dbo.Child WHERE ParentID = 1; --Now delete in Parent DELETE FROM dbo.Parent WHERE ID = 1; GO DROP TABLE dbo.Child; DROP TABLE dbo.Parent;上的第一次删除失败，因为它与外键约束冲突。但是，删除该ID中子级中的所有行之后，您可以删除父级行。

相同的逻辑适用于您的数据。首先删除子表中的相关行，然后删除父表中的数据。或者，实现级联，然后只需要删除父级中的行，删除操作就会向下层叠。

从2个具有外键约束的表中删除

2 个答案: