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  • 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。',16,1)
       END
     GO

    简单修改基本上可以解决所有SqlServer数据库级联删除和级联更新的问题

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  • 原文地址:https://www.cnblogs.com/wuliang/p/974194.html
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