如何在SQL Server中列出所有带有"WITH NOCHECK"的外键

有没有人知道一个查询列出了应用了"WITH NOCHECK"描述的数据库中的所有外键？(移除它们将提高性能和稳定性).

1> Nick Kavadia..：

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以下将返回当前数据库中禁用的外键名称,即WITH NOCHECK

对于SQL Server 2005/2008:

select * from sys.foreign_keys where is_disabled=1

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答案中有一些关于残疾与不信任之间差异的讨论.下面的内容解释了不同之处以下是一些代码,用于阐明is_disabled和isnotrusted之间的区别.

-- 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 表示禁用约束

isnottrusted 表示SQL Server不信任已针对外键表检查了列.

因此,不能假设将优化重新启用外键约束.为确保优化器信任该列,最好删除外键约束并使用WITH CHECK选项(4.)重新创建它.

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您可以使用以下代码重新启用约束并同时检查它:`ALTER TABLE t1 WITH CHECK CHECK CONSTRAINT fk_1`这比删除和重新创建约束要简单一些.

2> digiguru..：

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SELECT * FROM sys.foreign_keys AS f Where Is_Not_Trusted = 1

3> Scott Munro..：

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以下脚本将生成alter语句,这些语句将检查现有数据并防止对当前不受信任的外键的任何新违规('with nocheck').

在SQL Server Management Studio中执行它以生成脚本,然后将它们复制到查询窗口中以执行它们.

select
    'alter table ' + quotename(s.name) + '.' + quotename(t.name) + ' with check check constraint ' + fk.name +';'
from 
    sys.foreign_keys fk
inner join
    sys.tables t
on
    fk.parent_object_id = t.object_id
inner join
    sys.schemas s
on
    t.schema_id = s.schema_id
where 
    fk.is_not_trusted = 1

4> Mitch Wheat..：

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WITH NOCHECK只能暂时应用于FK,或者如链接文章所指出的那样对优化器无效.来自BOL:

查询优化器不考虑使用NOCHECK定义的约束.在使用ALTER TABLE表CHECK CONSTRAINT ALL重新启用这些约束之前,将忽略这些约束.

这将识别您的所有外键:(处理WITH NOCHECK位...)

SELECT C.TABLE_CATALOG [PKTABLE_QUALIFIER], 
       C.TABLE_SCHEMA [PKTABLE_OWNER], 
       C.TABLE_NAME [PKTABLE_NAME], 
       KCU.COLUMN_NAME [PKCOLUMN_NAME], 
       C2.TABLE_CATALOG [FKTABLE_QUALIFIER], 
       C2.TABLE_SCHEMA [FKTABLE_OWNER], 
       C2.TABLE_NAME [FKTABLE_NAME], 
       KCU2.COLUMN_NAME [FKCOLUMN_NAME], 
       RC.UPDATE_RULE, 
       RC.DELETE_RULE, 
       C.CONSTRAINT_NAME [FK_NAME], 
       C2.CONSTRAINT_NAME [PK_NAME], 
       CAST(7 AS SMALLINT) [DEFERRABILITY] 
FROM   INFORMATION_SCHEMA.TABLE_CONSTRAINTS C 
       INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU 
         ON C.CONSTRAINT_SCHEMA = KCU.CONSTRAINT_SCHEMA 
            AND C.CONSTRAINT_NAME = KCU.CONSTRAINT_NAME 
       INNER JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS RC 
         ON C.CONSTRAINT_SCHEMA = RC.CONSTRAINT_SCHEMA 
            AND C.CONSTRAINT_NAME = RC.CONSTRAINT_NAME 
       INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS C2 
         ON RC.UNIQUE_CONSTRAINT_SCHEMA = C2.CONSTRAINT_SCHEMA 
            AND RC.UNIQUE_CONSTRAINT_NAME = C2.CONSTRAINT_NAME 
       INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU2 
         ON C2.CONSTRAINT_SCHEMA = KCU2.CONSTRAINT_SCHEMA 
            AND C2.CONSTRAINT_NAME = KCU2.CONSTRAINT_NAME 
            AND KCU.ORDINAL_POSITION = KCU2.ORDINAL_POSITION 
WHERE  C.CONSTRAINT_TYPE = 'FOREIGN KEY'

参考.

另外,在SQL Server 2000和2005中,您可以使用以下命令检查是否有任何数据违反约束:

DBCC CHECKCONSTRAINTS (table_name)