Question

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）。

Answer 1

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

<小时/> 答案中有一些关于残疾人与健康人之间差异的讨论。不信任。以下是解释差异的原因这里有一些代码来澄清is_disabled和amp;之间的区别。 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表示禁用约束

isnottrusted表示SQL Server不信任已根据外键表检查了列。

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＆amp;使用WITH CHECK选项（4.）

重新创建它

Answer 2

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

Answer 3

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

Answer 4

WITH NOCHECK只能暂时应用于FK，否则它们会对链接文章指出对优化器无用。来自BOL：

查询优化器不考虑 WITH定义的约束 NOCHECK。这些约束被忽略了直到通过使用重新启用它们 ALTER TABLE表CHECK CONSTRAINT ALL。

这将标识所有外键:(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'

Ref

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

DBCC CHECKCONSTRAINTS (table_name)

Answer 5

以下代码检索标记为“WITH NOCHECK”的所有外键，然后使用ALTER语句对其进行修复：

-- configure cursor on all FKs with "WITH NOCHECK"
DECLARE UntrustedForeignKeysCursor CURSOR STATIC FOR
    SELECT  f.name,
            t.name 
    FROM    sys.foreign_keys AS f
            LEFT JOIN sys.tables AS t 
                ON f.parent_object_id = t.object_id 
    Where   Is_Not_Trusted = 1
OPEN UntrustedForeignKeysCursor

-- loop through the untrusted FKs
DECLARE @FKName varchar(100)
DECLARE @TableName varchar(100)
FETCH NEXT FROM UntrustedForeignKeysCursor INTO @FKName, @TableName
WHILE @@FETCH_STATUS = 0
BEGIN

    -- Rebuild the FK constraint WITH CHECK
    EXEC ('ALTER TABLE ' + @TableName + ' WITH CHECK CHECK CONSTRAINT ' + @FKName)

    -- get next user
    FETCH NEXT FROM UntrustedForeignKeysCursor INTO @FKName, @TableName

END

-- cleanup
CLOSE UntrustedForeignKeysCursor

Answer 6

我知道这是一个老问题，有一些旧的答案，有一些很好的信息。但是，我只是想分享一个脚本，我一直用它来解决这个问题领域的几个不同的数据库：

-- Foreign Keys
SELECT 'ALTER TABLE ' + o.name + ' WITH CHECK CHECK CONSTRAINT ' + i.name + ';' AS AlterStatement
from sys.foreign_keys i
INNER JOIN sys.objects o ON i.parent_object_id = o.object_id
INNER JOIN sys.schemas s ON o.schema_id = s.schema_id
WHERE i.is_not_trusted = 1 AND i.is_not_for_replication = 0;
GO

-- Constraints
SELECT 'ALTER TABLE ' + o.name + ' WITH CHECK CHECK CONSTRAINT ' + i.name + ';' AS AlterStatement
from sys.check_constraints i
INNER JOIN sys.objects o ON i.parent_object_id = o.object_id
INNER JOIN sys.schemas s ON o.schema_id = s.schema_id
WHERE i.is_not_trusted = 1 AND i.is_not_for_replication = 0 AND i.is_disabled = 0;
GO

这将生成一组ALTER语句来修复此问题＆＃34; NOCHECK＆＃34;外键和约束的问题。这是基于Brent Ozar提供的一些查询，但我为了我的目的和易用性进行了调整。这可以通过UNION轻松调整，以使其成为单个查询。

仅供参考，我在Azure SQL数据库环境中专门使用了它。我不确定旧版本的SQL Server是否存在限制，但它在Azure中运行良好。

如何在SQL Server中列出所有带有“WITH NOCHECK”的外键

6 个答案: