实现删除主表数据时, 判断与之关联的外键表是否有数据引用, 有标志, 无则删除

问题描述：

某个基础信息表，与系统中30多个表存在外键关系，当删除基础数据时，需要判断是否已经被用过，如果用过则更改标志位，如果没有用过则直接删除，如何能很好实现这个处理？最好能够自动适应表的变化

问题解决（SQL Server 2005）

-- SQL Server 2005的错误处理容易控制, 因此，SQL Server 2005中可以直接删除, 通过错误处理来确定是否需要更新.

-- 示例如下.

USE tempdb

GO

CREATE TABLE m(

id int PRIMARY KEY,

bz bit)

INSERT m SELECT 1, 0

UNION ALL SELECT 2, 0

CREATE TABLE c(

id int primary key,

a_id int references m(id)

ON DELETE NO ACTION)

INSERT c SELECT 1, 1

GO

-- 删除处理存储过程

CREATE PROC dbo.p_delete

@id int

AS

SET NOCOUNT ON

BEGIN TRY

BEGIN TRAN

DELETE FROM m WHERE id = @id

COMMIT TRAN

END TRY

BEGIN CATCH

ROLLBACK TRAN

IF ERROR_NUMBER() = 547 -- 如果是外键约束错误

BEGIN

BEGIN TRY

BEGIN TRAN -- 更新标志

UPDATE m SET bz = 1

WHERE id = @id

COMMIT TRAN

END TRY

BEGIN CATCH

SELECT ERROR_NUMBER(), ERROR_MESSAGE()

END CATCH

END

ELSE

SELECT ERROR_NUMBER(), ERROR_MESSAGE()

END CATCH

GO

-- 调用

EXEC dbo.p_delete 1

EXEC dbo.p_delete 2

SELECT * FROM m

SELECT * FROM c

GO

DROP TABLE c, m

DROP PROC dbo.p_delete

问题解决（SQL Server 2000）

-- SQL Server 2000 对错误处理不好控制, 一般还是建议做判断

-- 通过系统表查询系统表，可以获取某个表关联的所有外键表

-- 示例存储过程

CREATE PROC dbo.p_Delete

@tbname sysname, -- 基础数据表名

@PkFieldName sysname, -- 基础数据表关键字段名

@PkValue int -- 要删除的基础数据表关键字值

AS

SET NOCOUNT ON

DECLARE @bz bit, @s nvarchar(4000)

DECLARE tb CURSOR LOCAL

FOR

SELECT N'

SET @bz = CASE WHEN EXISTS(

SELECT * FROM ' + QUOTENAME(@tbname)

+ N' A, ' + QUOTENAME(OBJECT_NAME(B.fkeyid))

+ N' B

WHERE A.' + QUOTENAME((SELECT name FROM syscolumns WHERE colid = B.rkey AND id = B.rkeyid))

+ N' = B.' + QUOTENAME((SELECT name FROM syscolumns WHERE colid = B.fkey AND id = B.fkeyid))

+ N' AND A.' + QUOTENAME((SELECT name FROM syscolumns WHERE colid = B.rkey AND id = B.rkeyid))

+ N' = @id) THEN 1 ELSE 0 END'

FROM sysobjects A

JOIN sysforeignkeys B

ON A.id=B.constid

JOIN sysobjects C

ON A.parent_obj = C.id

WHERE A.xtype = 'f'

AND C.xtype = 'U'

AND OBJECT_NAME(B.rkeyid) = @tbname

OPEN tb

FETCH tb INTO @s

WHILE @@FETCH_STATUS = 0

BEGIN

EXEC sp_executesql @s, N'@tbname sysname, @id int, @bz bit OUT', @tbname, @PkValue, @bz OUT

IF @bz = 1

BEGIN

SET @s = N'UPDATE ' + QUOTENAME(@tbname)

+ N' SET bz = 1 WHERE ' + QUOTENAME(@PkFieldName)

+ N' = @id'

EXEC sp_executesql @s, N'@id int', @PkValue

RETURN

END

FETCH tb INTO @s

END

CLOSE tb

DEALLOCATE tb

SET @s = N'DELETE FROM ' + QUOTENAME(@tbname)

+ N' WHERE ' + QUOTENAME(@PkFieldName)

+ N' = @id'

EXEC sp_executesql @s, N'@id int', @PkValue

GO

注意事项

设置表的主/外键关系的时候，不要设置级联删除（ON DELETE CASCADE）