如何使用“WITH NOCHECK"列出所有外键在 SQL Server 中 [英] How to list out all Foreign Keys with "WITH NOCHECK" in SQL Server

问题描述

有没有人知道一个查询列出了数据库中所有外键并应用了 WITH NOCHECK 描述的查询?(删除它们将提高性能和稳定性).

Does anyone know a query for listing out all foreign keys in a database with WITH NOCHECK description applied to it? (removing them will boost performance and stability).

推荐答案

以下将返回当前数据库中被禁用的外键的名称，即 WITH NOCHECK

The following will return the name of the foreign keys in the current database that are disabled i.e. WITH NOCHECK

对于 SQL Server 2005/2008:

For SQL Server 2005/2008:

select * from sys.foreign_keys where is_disabled=1

<小时>关于disabled & 之间的区别的答案中有一些讨论.不信任.以下内容解释了差异这是一些代码来阐明 is_disabled 和之间的区别不受信任.

---

There was some discussion in the answer about the difference between disabled & not trusted. What's below explains the differnce Here's some code to clarify the difference between is_disabled & isnotrusted.

-- drop table t1
-- drop table t2
create table t1(i int not null, fk int not null)
create table t2(i int not null)
-- create primary key on t2
alter table t2
add constraint pk_1 primary key (i)
-- create foriegn key on t1
alter table t1
add constraint fk_1 foreign key (fk)
    references t2 (i)
--insert some records
insert t2 values(100)
insert t2 values(200)
insert t2 values(300)
insert t2 values(400)
insert t2 values(500)
insert t1 values(1,100)
insert t1 values(2,100)
insert t1 values(3,500)
insert t1 values(4,500)
----------------------------
-- 1. enabled and trusted
select name,is_disabled,is_not_trusted from sys.foreign_keys
GO

-- 2. disable the constraint
alter table t1 NOCHECK CONSTRAINT fk_1
select name,is_disabled,is_not_trusted from sys.foreign_keys
GO

-- 3. re-enable constraint, data isnt checked, so not trusted.
-- this means the optimizer will still have to check the column
alter table  t1 CHECK CONSTRAINT fk_1 
select name,is_disabled,is_not_trusted from sys.foreign_keys
GO

--4. drop the foreign key constraint & re-add 
-- it making sure its checked
-- constraint is then enabled and trusted
alter table t1  DROP CONSTRAINT fk_1
alter table t1 WITH CHECK 
add constraint fk_1 foreign key (fk)
    references t2 (i)
select name,is_disabled,is_not_trusted from sys.foreign_keys
GO


--5. drop the foreign key constraint & add but dont check
-- constraint is then enabled, but not trusted
alter table t1  DROP CONSTRAINT fk_1
alter table t1 WITH NOCHECK 
add constraint fk_1 foreign key (fk)
    references t2 (i)
select name,is_disabled,is_not_trusted from sys.foreign_keys
GO

is_disabled 表示约束被禁用

isnottrusted 表示 SQL Server 不相信该列已针对外键表进行了检查.

isnottrusted means that SQL Server does not trust that the column has been checked against the foreign key table.

因此，不能假设重新启用外键约束会得到优化.为确保优化器信任该列，最好删除外键约束 &使用 WITH CHECK 选项重新创建它 (4.)

Thus it cannot be assumed that re-enabling the foreign key constraint will be optimized. To ensure the optimizer trusts the column, it's best to drop the foreign key constraint & re-create it with the WITH CHECK option (4.)

这篇关于如何使用“WITH NOCHECK"列出所有外键在 SQL Server 中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！