使用MSSQL2005，如果我首先截断子表(具有FK关系的主键的表)，我可以截断带有外键约束的表吗?
我知道我也可以
使用不带where子句的DELETE，然后RESEED标识(或) 删除FK，截断表，并重新创建FK。
我认为只要我在父表之前截断子表，我就可以不做上面的任何一个选项，但我得到了这个错误:
不能截断表'TableName'，因为它被一个FOREIGN KEY约束引用。
当前回答
这是我对这个问题的解决方案。我用它来改变PK，但想法是一样的。希望这将是有用的)
PRINT 'Script starts'
DECLARE @foreign_key_name varchar(255)
DECLARE @keycnt int
DECLARE @foreign_table varchar(255)
DECLARE @foreign_column_1 varchar(255)
DECLARE @foreign_column_2 varchar(255)
DECLARE @primary_table varchar(255)
DECLARE @primary_column_1 varchar(255)
DECLARE @primary_column_2 varchar(255)
DECLARE @TablN varchar(255)
-->> Type the primary table name
SET @TablN = ''
--------------------------------------------------------------------------------------- ------------------------------
--Here will be created the temporary table with all reference FKs
---------------------------------------------------------------------------------------------------------------------
PRINT 'Creating the temporary table'
select cast(f.name as varchar(255)) as foreign_key_name
, r.keycnt
, cast(c.name as varchar(255)) as foreign_table
, cast(fc.name as varchar(255)) as foreign_column_1
, cast(fc2.name as varchar(255)) as foreign_column_2
, cast(p.name as varchar(255)) as primary_table
, cast(rc.name as varchar(255)) as primary_column_1
, cast(rc2.name as varchar(255)) as primary_column_2
into #ConTab
from sysobjects f
inner join sysobjects c on f.parent_obj = c.id
inner join sysreferences r on f.id = r.constid
inner join sysobjects p on r.rkeyid = p.id
inner join syscolumns rc on r.rkeyid = rc.id and r.rkey1 = rc.colid
inner join syscolumns fc on r.fkeyid = fc.id and r.fkey1 = fc.colid
left join syscolumns rc2 on r.rkeyid = rc2.id and r.rkey2 = rc.colid
left join syscolumns fc2 on r.fkeyid = fc2.id and r.fkey2 = fc.colid
where f.type = 'F' and p.name = @TablN
ORDER BY cast(p.name as varchar(255))
---------------------------------------------------------------------------------------------------------------------
--Cursor, below, will drop all reference FKs
---------------------------------------------------------------------------------------------------------------------
DECLARE @CURSOR CURSOR
/*Fill in cursor*/
PRINT 'Cursor 1 starting. All refernce FK will be droped'
SET @CURSOR = CURSOR SCROLL
FOR
select foreign_key_name
, keycnt
, foreign_table
, foreign_column_1
, foreign_column_2
, primary_table
, primary_column_1
, primary_column_2
from #ConTab
OPEN @CURSOR
FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2,
@primary_table, @primary_column_1, @primary_column_2
WHILE @@FETCH_STATUS = 0
BEGIN
EXEC ('ALTER TABLE ['+@foreign_table+'] DROP CONSTRAINT ['+@foreign_key_name+']')
FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2,
@primary_table, @primary_column_1, @primary_column_2
END
CLOSE @CURSOR
PRINT 'Cursor 1 finished work'
---------------------------------------------------------------------------------------------------------------------
--Here you should provide the chainging script for the primary table
---------------------------------------------------------------------------------------------------------------------
PRINT 'Altering primary table begin'
TRUNCATE TABLE table_name
PRINT 'Altering finished'
---------------------------------------------------------------------------------------------------------------------
--Cursor, below, will add again all reference FKs
--------------------------------------------------------------------------------------------------------------------
PRINT 'Cursor 2 starting. All refernce FK will added'
SET @CURSOR = CURSOR SCROLL
FOR
select foreign_key_name
, keycnt
, foreign_table
, foreign_column_1
, foreign_column_2
, primary_table
, primary_column_1
, primary_column_2
from #ConTab
OPEN @CURSOR
FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2,
@primary_table, @primary_column_1, @primary_column_2
WHILE @@FETCH_STATUS = 0
BEGIN
EXEC ('ALTER TABLE [' +@foreign_table+ '] WITH NOCHECK ADD CONSTRAINT [' +@foreign_key_name+ '] FOREIGN KEY(['+@foreign_column_1+'])
REFERENCES [' +@primary_table+'] (['+@primary_column_1+'])')
EXEC ('ALTER TABLE [' +@foreign_table+ '] CHECK CONSTRAINT [' +@foreign_key_name+']')
FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2,
@primary_table, @primary_column_1, @primary_column_2
END
CLOSE @CURSOR
PRINT 'Cursor 2 finished work'
---------------------------------------------------------------------------------------------------------------------
PRINT 'Temporary table droping'
drop table #ConTab
PRINT 'Finish'
其他回答
你可以按照这个步骤来做， 通过重新播种表，可以删除表中的数据。
delete from table_name
dbcc checkident('table_name',reseed,0)
如果出现错误，则必须重新播种主表。
正确的;你不能截断一个有FK约束的表。
通常我的处理方法是:
去掉约束 截断表格 重新创建约束。
(当然，这一切都在一笔交易中。)
当然，这只适用于子节点已经被截断的情况。否则，我会走不同的路线，完全取决于我的数据是什么样子的。(变量太多，不便在此赘述。)
最初的海报决定了为什么会这样;更多细节请看这个答案。
这是我对这个问题的解决方案。我用它来改变PK，但想法是一样的。希望这将是有用的)
PRINT 'Script starts'
DECLARE @foreign_key_name varchar(255)
DECLARE @keycnt int
DECLARE @foreign_table varchar(255)
DECLARE @foreign_column_1 varchar(255)
DECLARE @foreign_column_2 varchar(255)
DECLARE @primary_table varchar(255)
DECLARE @primary_column_1 varchar(255)
DECLARE @primary_column_2 varchar(255)
DECLARE @TablN varchar(255)
-->> Type the primary table name
SET @TablN = ''
--------------------------------------------------------------------------------------- ------------------------------
--Here will be created the temporary table with all reference FKs
---------------------------------------------------------------------------------------------------------------------
PRINT 'Creating the temporary table'
select cast(f.name as varchar(255)) as foreign_key_name
, r.keycnt
, cast(c.name as varchar(255)) as foreign_table
, cast(fc.name as varchar(255)) as foreign_column_1
, cast(fc2.name as varchar(255)) as foreign_column_2
, cast(p.name as varchar(255)) as primary_table
, cast(rc.name as varchar(255)) as primary_column_1
, cast(rc2.name as varchar(255)) as primary_column_2
into #ConTab
from sysobjects f
inner join sysobjects c on f.parent_obj = c.id
inner join sysreferences r on f.id = r.constid
inner join sysobjects p on r.rkeyid = p.id
inner join syscolumns rc on r.rkeyid = rc.id and r.rkey1 = rc.colid
inner join syscolumns fc on r.fkeyid = fc.id and r.fkey1 = fc.colid
left join syscolumns rc2 on r.rkeyid = rc2.id and r.rkey2 = rc.colid
left join syscolumns fc2 on r.fkeyid = fc2.id and r.fkey2 = fc.colid
where f.type = 'F' and p.name = @TablN
ORDER BY cast(p.name as varchar(255))
---------------------------------------------------------------------------------------------------------------------
--Cursor, below, will drop all reference FKs
---------------------------------------------------------------------------------------------------------------------
DECLARE @CURSOR CURSOR
/*Fill in cursor*/
PRINT 'Cursor 1 starting. All refernce FK will be droped'
SET @CURSOR = CURSOR SCROLL
FOR
select foreign_key_name
, keycnt
, foreign_table
, foreign_column_1
, foreign_column_2
, primary_table
, primary_column_1
, primary_column_2
from #ConTab
OPEN @CURSOR
FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2,
@primary_table, @primary_column_1, @primary_column_2
WHILE @@FETCH_STATUS = 0
BEGIN
EXEC ('ALTER TABLE ['+@foreign_table+'] DROP CONSTRAINT ['+@foreign_key_name+']')
FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2,
@primary_table, @primary_column_1, @primary_column_2
END
CLOSE @CURSOR
PRINT 'Cursor 1 finished work'
---------------------------------------------------------------------------------------------------------------------
--Here you should provide the chainging script for the primary table
---------------------------------------------------------------------------------------------------------------------
PRINT 'Altering primary table begin'
TRUNCATE TABLE table_name
PRINT 'Altering finished'
---------------------------------------------------------------------------------------------------------------------
--Cursor, below, will add again all reference FKs
--------------------------------------------------------------------------------------------------------------------
PRINT 'Cursor 2 starting. All refernce FK will added'
SET @CURSOR = CURSOR SCROLL
FOR
select foreign_key_name
, keycnt
, foreign_table
, foreign_column_1
, foreign_column_2
, primary_table
, primary_column_1
, primary_column_2
from #ConTab
OPEN @CURSOR
FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2,
@primary_table, @primary_column_1, @primary_column_2
WHILE @@FETCH_STATUS = 0
BEGIN
EXEC ('ALTER TABLE [' +@foreign_table+ '] WITH NOCHECK ADD CONSTRAINT [' +@foreign_key_name+ '] FOREIGN KEY(['+@foreign_column_1+'])
REFERENCES [' +@primary_table+'] (['+@primary_column_1+'])')
EXEC ('ALTER TABLE [' +@foreign_table+ '] CHECK CONSTRAINT [' +@foreign_key_name+']')
FETCH NEXT FROM @CURSOR INTO @foreign_key_name, @keycnt, @foreign_table, @foreign_column_1, @foreign_column_2,
@primary_table, @primary_column_1, @primary_column_2
END
CLOSE @CURSOR
PRINT 'Cursor 2 finished work'
---------------------------------------------------------------------------------------------------------------------
PRINT 'Temporary table droping'
drop table #ConTab
PRINT 'Finish'
对于MS SQL，至少在更新的版本中，你可以通过如下代码禁用约束:
ALTER TABLE Orders
NOCHECK CONSTRAINT [FK_dbo.Orders_dbo.Customers_Customer_Id]
GO
TRUNCATE TABLE Customers
GO
ALTER TABLE Orders
WITH CHECK CHECK CONSTRAINT [FK_dbo.Orders_dbo.Customers_Customer_Id]
GO
您可以尝试DELETE FROM <您的表>;。
服务器将向您显示限制的名称和表，删除该表可以删除所需的内容。
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