如何在 SQL Server 中列出所有带有“WITH NOCHECK”的外键

Question

有没有人知道一个查询来列出数据库中的所有外键并应用WITH NOCHECK 描述？ （删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被禁用的外键的名称，即 WITH NOCHECK

对于 SQL Server 2005/2008：

select * from sys.foreign_keys where is_disabled=1

---

答案中有一些关于禁用和不信任之间的区别的讨论。 以下内容解释了差异 这是一些代码来阐明 is_disabled 和 isnottrusted 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。

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，最好删除外键约束并使用 WITH CHECK 选项重新创建它 (4.)

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当前不受信任的外键（'with nocheck'）的任何新违规行为。

在 SQL Server Management Studio 中执行以生成脚本，然后将它们复制到查询窗口中执行。

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，否则正如您链接的文章所指出的那样，它们对优化器毫无用处。来自 BOL：

查询优化器不考虑 WITH 定义的约束 诺查克。此类约束被忽略 直到它们通过使用重新启用 ALTER TABLE 表检查约束 全部。

这将识别您所有的外键：（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.

顺便说一句，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

以下代码检索所有标记为“WITH NOCHECK”的外键，然后使用 ALTER 语句修复它们：

-- 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，我一直在使用它来为我们解决很多不同的数据库中的这个问题：

-- 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，以解决外键和约束的“NOCHECK”问题。这是基于Brent Ozar 提供的一些查询，但我出于我的目的和易用性进行了调整。这可以通过 UNION 轻松调整，使其成为单个查询。

仅供参考，我只在 Azure SQL 数据库环境中使用过它。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。