SQL Server支持禁用和启用外键约束吗?还是我唯一的选择就是放弃这些限制,然后重新创造这些限制?
当前回答
如果你感兴趣,我有一个更有用的版本。我从这里提取了一些代码,一个网站的链接不再活跃。我修改了它,以允许存储过程中有一个表数组,并在执行所有语句之前填充删除、截断和添加语句。这使您可以控制决定哪些表需要截断。
/****** Object: UserDefinedTableType [util].[typ_objects_for_managing] Script Date: 03/04/2016 16:42:55 ******/
CREATE TYPE [util].[typ_objects_for_managing] AS TABLE(
[schema] [sysname] NOT NULL,
[object] [sysname] NOT NULL
)
GO
create procedure [util].[truncate_table_with_constraints]
@objects_for_managing util.typ_objects_for_managing readonly
--@schema sysname
--,@table sysname
as
--select
-- @table = 'TABLE',
-- @schema = 'SCHEMA'
declare @exec_table as table (ordinal int identity (1,1), statement nvarchar(4000), primary key (ordinal));
--print '/*Drop Foreign Key Statements for ['+@schema+'].['+@table+']*/'
insert into @exec_table (statement)
select
'ALTER TABLE ['+SCHEMA_NAME(o.schema_id)+'].['+ o.name+'] DROP CONSTRAINT ['+fk.name+']'
from sys.foreign_keys fk
inner join sys.objects o
on fk.parent_object_id = o.object_id
where
exists (
select * from @objects_for_managing chk
where
chk.[schema] = SCHEMA_NAME(o.schema_id)
and
chk.[object] = o.name
)
;
--o.name = @table and
--SCHEMA_NAME(o.schema_id) = @schema
insert into @exec_table (statement)
select
'TRUNCATE TABLE ' + src.[schema] + '.' + src.[object]
from @objects_for_managing src
;
--print '/*Create Foreign Key Statements for ['+@schema+'].['+@table+']*/'
insert into @exec_table (statement)
select 'ALTER TABLE ['+SCHEMA_NAME(o.schema_id)+'].['+o.name+'] ADD CONSTRAINT ['+fk.name+'] FOREIGN KEY (['+c.name+'])
REFERENCES ['+SCHEMA_NAME(refob.schema_id)+'].['+refob.name+'](['+refcol.name+'])'
from sys.foreign_key_columns fkc
inner join sys.foreign_keys fk
on fkc.constraint_object_id = fk.object_id
inner join sys.objects o
on fk.parent_object_id = o.object_id
inner join sys.columns c
on fkc.parent_column_id = c.column_id and
o.object_id = c.object_id
inner join sys.objects refob
on fkc.referenced_object_id = refob.object_id
inner join sys.columns refcol
on fkc.referenced_column_id = refcol.column_id and
fkc.referenced_object_id = refcol.object_id
where
exists (
select * from @objects_for_managing chk
where
chk.[schema] = SCHEMA_NAME(o.schema_id)
and
chk.[object] = o.name
)
;
--o.name = @table and
--SCHEMA_NAME(o.schema_id) = @schema
declare @looper int , @total_records int, @sql_exec nvarchar(4000)
select @looper = 1, @total_records = count(*) from @exec_table;
while @looper <= @total_records
begin
select @sql_exec = (select statement from @exec_table where ordinal =@looper)
exec sp_executesql @sql_exec
print @sql_exec
set @looper = @looper + 1
end
其他回答
找到约束条件
SELECT *
FROM sys.foreign_keys
WHERE referenced_object_id = object_id('TABLE_NAME')
执行由此SQL生成的SQL
SELECT
'ALTER TABLE ' + OBJECT_SCHEMA_NAME(parent_object_id) +
'.[' + OBJECT_NAME(parent_object_id) +
'] DROP CONSTRAINT ' + name
FROM sys.foreign_keys
WHERE referenced_object_id = object_id('TABLE_NAME')
西夫韦。
注意:增加了删除约束的解决方案,这样可以删除或修改表而没有任何约束错误。
右键单击表设计,进入“关系”,在左侧窗格中选择外键,在右侧窗格中,将强制外键约束设置为“Yes”(启用外键约束)或“No”(禁用外键约束)。
一个脚本来管理它们:这个脚本将截断和删除命令与sp_MSforeachtable结合在一起,这样您就可以避免删除和重新创建约束——只需指定需要删除而不是截断的表,为了便于度量,我还包含了一个额外的模式过滤器(在2008r2中测试)。
declare @schema nvarchar(max) = 'and Schema_Id=Schema_id(''Value'')'
declare @deletiontables nvarchar(max) = '(''TableA'',''TableB'')'
declare @truncateclause nvarchar(max) = @schema + ' and o.Name not in ' + + @deletiontables;
declare @deleteclause nvarchar(max) = @schema + ' and o.Name in ' + @deletiontables;
exec sp_MSforeachtable 'alter table ? nocheck constraint all', @whereand=@schema
exec sp_MSforeachtable 'truncate table ?', @whereand=@truncateclause
exec sp_MSforeachtable 'delete from ?', @whereand=@deleteclause
exec sp_MSforeachtable 'alter table ? with check check constraint all', @whereand=@schema
(摘自http://www.sqljunkies.com/WebLog/roman/archive/2005/01/30/7037.aspx, 现在存档在时光倒流机中)
Foreign key constraints and check constraint are very useful for enforcing data integrity and business rules. There are certain scenarios though where it is useful to temporarily turn them off because their behavior is either not needed or could do more harm than good. I sometimes disable constraint checking on tables during data loads from external sources or when I need to script a table drop/recreate with reloading the data back into the table. I usually do it in scenarios where I don't want a time consuming process to fail because one or a few of many million rows have bad data in it. But I always turn the constraints back on once the process is finished and also in some cases I run data integrity checks on the imported data.
如果禁用外键约束,则可以插入父表中不存在的值。如果禁用检查约束,则可以将值放入列中,就像检查约束不存在一样。下面是禁用和启用表约束的一些例子:
——禁用所有表约束 修改表MyTable NOCHECK约束 ——启用所有表约束 修改MyTable,检查检查约束全部 ——禁用单个约束 修改表MyTable NOCHECK约束 ——启用单一约束 ALTER TABLE MyTable WITH CHECK CHECK CONSTRAINT MyConstraint
如果你想禁用数据库中的所有约束,只需运行以下代码:
-- disable all constraints
EXEC sp_MSforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT all"
要将它们重新打开,运行:(打印当然是可选的,它只是列出表)
-- enable all constraints
exec sp_MSforeachtable @command1="print '?'", @command2="ALTER TABLE ? WITH CHECK CHECK CONSTRAINT all"
我发现它在将数据从一个数据库填充到另一个数据库时很有用。这是比放弃约束更好的方法。正如您所提到的,当删除数据库中的所有数据并重新填充它时(例如在测试环境中),它非常方便。
如果您正在删除所有数据,您可能会发现这个解决方案是有用的。
有时禁用所有触发器也很方便,你可以在这里看到完整的解决方案。
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