转：SQLServer级联删除示例

SQLServer 2000与Oracle 8i相比较，在级联删除上有太多的限制

1. 表内自关联不支持级联删除和级联更新
2. 一个表内在有多个列同时关联于另一个表时，不支持多个级联删除
3. 还有什么循环级联删除限制，等等
4. .......

一大堆限制，如果要迁移Oracle到SqlServer麻烦多多，特别对于用于构造树型结构的表内自关联（比如部门表）的级联删除特别讨厌

考虑来考虑去，对于SqlServer不能支持的诸多级联删除只有采用最原始的方法，彻底不用外键关联，而是用触发器来解决

以下是经过验证的触发器实现范例（自关联例子）

放弃外键关联后所有的完整性检查都要通过触发器实现

--DELETE 级联删除，先删除，再删除所有级联的记录，采用递归触发器，当然要求数据库支持递归触发器功能开启（数据库属性设置中开启他），不过SqlServer只支持32级的递归啊
?IF EXISTS (SELECT NAME FROM SYSOBJECTS
????? WHERE NAME = 'DEL_DOCUMENTTYPE_001' AND TYPE = 'TR')
?? DROP TRIGGER DEL_DOCUMENTTYPE_001
?GO
?
?CREATE TRIGGER DEL_DOCUMENTTYPE_001
?ON dbo.DOCUMENTTYPE
?FOR DELETE
?AS?
?IF (SELECT COUNT(*) FROM DELETED) > 0
?? DELETE FROM dbo.DOCUMENTTYPE WHERE UPNO IN (SELECT NO FROM DELETED)
?GO???
??

?

--INSERT? 数据插入，验证外键关联逻辑，错误抛出出错信息
?IF EXISTS (SELECT NAME FROM SYSOBJECTS
????? WHERE NAME = 'INS_DOCUMENTTYPE_001' AND TYPE = 'TR')
?? DROP TRIGGER INS_DOCUMENTTYPE_001
?GO
?
?CREATE TRIGGER INS_DOCUMENTTYPE_001
?ON dbo.DOCUMENTTYPE
?FOR INSERT
?AS?
?IF (SELECT COUNT(*) FROM INSERTED WHERE UPNO IS NOT NULL
????? AND (UPNO = NO OR UPNO NOT IN (SELECT NO FROM dbo.DOCUMENTTYPE))) > 0
?? BEGIN
??? DELETE FROM dbo.DOCUMENTTYPE WHERE NO IN (SELECT NO FROM INSERTED)
??? RAISERROR('在被引用表 dbo.DOCUMENTTYPE 中没有与外键 UPNO 的引用列的列表匹配的主键或候选键。',16,1)
?? END
?GO?
??
--UPDATE? 数据更新，如果更新了外键，验证外键存在?IF EXISTS (SELECT NAME FROM SYSOBJECTS????? WHERE NAME = 'UPD_DOCUMENTTYPE_001' AND TYPE = 'TR')?? DROP TRIGGER UPD_DOCUMENTTYPE_001?GO??CREATE TRIGGER UPD_DOCUMENTTYPE_001?ON dbo.DOCUMENTTYPE?FOR UPDATE ?AS? ?IF (SELECT COUNT(*) FROM INSERTED WHERE UPNO IS NOT NULL ????? AND (UPNO = NO OR UPNO NOT IN (SELECT NO FROM dbo.DOCUMENTTYPE))) > 0?? BEGIN?????????? SET IDENTITY_INSERT dbo.DOCUMENTTYPE ON??? DELETE FROM dbo.DOCUMENTTYPE WHERE NO IN (SELECT NO FROM INSERTED)--??? INSERT INTO dbo.DOCUMENTTYPE SELECT * FROM INSERTED??? SELECT * INTO dbo.DOCUMENTTYPE FROM INSERTED??? SET IDENTITY_INSERT dbo.DOCUMENTTYPE OFF??? RAISERROR('在被引用表 dbo.DOCUMENTTYPE 中没有与外键 UPNO 的引用列的列表匹配的主键或候选键。',1)?? END?GO

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!