无法创建FK约束

Question

我有2张桌子:

TableA
------
TableAID INT IDENTITY Primary Key
TableBID INT NULL

I add a unique constraint on TableBID
ALTER TABLE TableAID ADD CONSTRAINT xx UNIQUE ([TableBID])

TableB
------
TableBID INT IDENTITY Primary Key

现在当我删除TableA行时,我也需要删除TableB,所以我试图添加一个带有级联删除的FK

ALTER TABLE TableB ADD CONSTRAINT yy FOREIGN KEY (TableBID) 
REFERENCES TableA (TABLEBID) ON DELETE CASCADE

但我得到这个错误:

Msg 1788, Level 16, State 0, Line 1
Cascading foreign key 'yy' cannot be created where the referencing column 'TableB.TableBID' is an identity column.

Answer 1

TableB.TableBID不能同时是IDENTITY列(独立计算),同时也是另一个表中列的外键.

我认为你的关系已经逆转并且实际上想要:

ALTER TABLE TableA ADD CONSTRAINT yy FOREIGN KEY (TableBID) 
REFERENCES TableB (TABLEBID) ON DELETE CASCADE