如何使外键约束受信任？

Question

我有两张桌子,销售和产品.Sale具有引用Product的外键约束.创建外键并在创建WITH NOCHECK后立即禁用.我想启用并信任外键约束.启用它可以工作但我不能让它被信任.

StackOverflow和各种博客上的类似问题表明运行ALTER TABLE T WITH CHECK CHECK CONSTRAINT C应该导致is_disabled=0和is_not_trusted=0,但is_not_trusted对我来说总是1.我究竟做错了什么？

我试图将示例代码放在SQL Fiddle上,但它不喜欢"DBCC"命令,所以这里是:

-- "_Scratch" is just a sandbox DB that I use for testing stuff.
USE _Scratch

CREATE TABLE dbo.Product
(
  ProductKeyId INT PRIMARY KEY NOT NULL,
  Description VARCHAR(40) NOT NULL
)

CREATE TABLE dbo.Sale
(
  ProductKeyId INT NOT NULL,
  SaleTime DATETIME NOT NULL,
  Value MONEY NOT NULL
)

ALTER TABLE dbo.Sale WITH NOCHECK
  ADD CONSTRAINT FK_Product_ProductKeyId FOREIGN KEY (ProductKeyId)
  REFERENCES dbo.Product (ProductKeyId) NOT FOR REPLICATION;

ALTER TABLE dbo.Sale NOCHECK CONSTRAINT FK_Product_ProductKeyId

INSERT INTO dbo.Product VALUES (1, 'Food')
INSERT INTO dbo.Sale VALUES (1, GETDATE(), 1.00)

-- Check the disabled/trusted state
SELECT name, is_disabled, is_not_trusted
FROM sys.foreign_keys
WHERE name = 'FK_Product_ProductKeyId'

  -- name                     is_disabled  is_not_trusted
  -- FK_Product_ProductKeyId  1            1

-- Check the FK_Product_ProductKeyId constraint
DBCC CHECKCONSTRAINTS('FK_Product_ProductKeyId')

  -- DBCC execution completed.
  -- If DBCC printed error messages, contact your system administrator.

-- Check all constraints on Sale table
DBCC CHECKCONSTRAINTS('Sale')

  -- DBCC execution completed.
  -- If DBCC printed error messages, contact your system administrator.

-- Add the constraint and check existing data
ALTER TABLE Sale WITH CHECK CHECK CONSTRAINT FK_Product_ProductKeyId

-- Check the disabled/trusted state
SELECT name, is_disabled, is_not_trusted
FROM sys.foreign_keys
WHERE name = 'FK_Product_ProductKeyId'

  -- name                     is_disabled  is_not_trusted
  -- FK_Product_ProductKeyId  0            1

-- Check the FK_Product_ProductKeyId constraint
DBCC CHECKCONSTRAINTS('FK_Product_ProductKeyId')

  -- DBCC execution completed.
  -- If DBCC printed error messages, contact your system administrator.

-- Check all constraints on Sale table
DBCC CHECKCONSTRAINTS('Sale')

  -- DBCC execution completed.
  -- If DBCC printed error messages, contact your system administrator.

Answer 1

根据您的示例,我也尝试过:

• 删除并重新创建外键.
• 删除并重新创建表.

然后我注意到命令中有一些东西:

NOT FOR REPLICATION

看起来如果使用NOT FOR REPLICATION创建约束,它始终不受信任.

从在线书籍引用:

在某些情况下,希望复制拓扑中的用户活动与代理活动的处理方式不同.例如,如果用户在发布服务器上插入了一行,并且该插入符合表上的检查约束,则在订阅服务器上由复制代理插入行时,可能不需要强制执行相同的约束.NOT FOR REPLICATION选项允许您指定在复制代理执行操作时以下方式处理以下数据库对象:

外键约束

当复制代理执行插入,更新或删除操作时,不会强制执行外键约束.

看起来该IS_NOT_TRUSTED设置仅与受影响的复制相关IS_NOT_FOR_REPLICATION.我想只要在您正在处理的服务器上强制执行约束,它应该没问题.所以我继续并证实了这一点:

SELECT name, is_disabled, is_not_trusted
FROM sys.foreign_keys
WHERE name = 'FK_Product_ProductKeyId'

name                    is_disabled is_not_trusted
FK_Product_ProductKeyId 0            1

INSERT INTO dbo.Sale VALUES (2, GETDATE(), 1.00)

Msg 547, Level 16, State 0, Line 1
The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Product_ProductKeyId". The conflict occurred in database "_Scratch", table "dbo.Product", column 'ProductKeyId'.
The statement has been terminated.

如果你仍然想要IS_NOT_TRUSTED = 0安心,只需重新创建外键NOT FOR REPLICATION.

如果你们想知道,我已经验证了对CHECK约束的相同效果.