更改外键的引用索引

我有这样的事情：

CREATE TABLE T1 (
    Id INT
    ...
    ,Constraint [PK_T1] PRIMARY KEY CLUSTERED [Id]
)

CREATE TABLE T2 (
    ....
    ,T1_Id INT NOT NULL
    ,CONSTRAINT [FK_T2_T1] FOREIGN KEY (T1_Id) REFERENCES T1(Id)
)

出于性能（和死锁）的原因，我在T1上创建了一个新索引

CREATE UNIQUE NONCLUSTERED INDEX IX_T1_Id ON T1 (Id)

但是，如果我检查哪个索引引用了FK，则继续引用聚集索引

select
    ix.index_id,
    ix.name as index_name,
    ix.type_desc as index_type_desc,
    fk.name as fk_name
from sys.indexes ix
    left join sys.foreign_keys fk on
        fk.referenced_object_id = ix.object_id
        and fk.key_index_id = ix.index_id
        and fk.parent_object_id = object_id('T2')
where ix.object_id = object_id('T1');

如果我删除约束并再次创建，它将引用非聚集索引，但这会导致再次检查所有t2 FK。

有没有一种方法可以更改此设置，以便FK_T2_T1使用IX_T1_Id而不是PK_T1而不删除FK并将表锁定在FK检查上？

谢谢！

好吧，继续搜索后，我发现了这篇文章

与普通查询不同，由于更新统计信息，创建新索引甚至重启服务器，它不会选择新索引。我知道将FK绑定到其他索引的唯一方法是删除并重新创建FK，让它自动选择索引，而没有手动控制它的选项。

因此，除非有人可以说，否则我将不得不寻找时间窗口来执行此任务。

谢谢

在这里阅读MS DOCS之后。

修改外键

若要使用Transact-SQL修改FOREIGN KEY约束，必须首先删除现有的FOREIGN KEY约束，然后使用新定义重新创建它。有关更多信息，请参见删除外键关系和创建外键关系。

如果您相信我，请添加一个新的FK并删除旧的FK。要禁用扫描，您可以使用NO CHECK选项

--DROP TABLE T2
--DROP TABLE T1


CREATE TABLE T1 (
    [Id] INT,
    [NAME] varchar(100), CONSTRAINT [PK_T1] PRIMARY KEY CLUSTERED (id))

CREATE TABLE T2 (
    t2_id int,
    T1_Id INT NOT NULL
    ,CONSTRAINT [FK_T2_T1] FOREIGN KEY (T1_Id) REFERENCES T1(Id)
)


CREATE UNIQUE NONCLUSTERED INDEX IX_T1_Id ON T1 (Id)


select
    ix.index_id,
    ix.name as index_name,
    ix.type_desc as index_type_desc,
    fk.name as fk_name
from sys.indexes ix
    left join sys.foreign_keys fk on
        fk.referenced_object_id = ix.object_id
        and fk.key_index_id = ix.index_id
        and fk.parent_object_id = object_id('T2')
where ix.object_id = object_id('T1');



╔══════════╦════════════╦═════════════════╦══════════╗
║ index_id ║ index_name ║ index_type_desc ║ fk_name  ║
╠══════════╬════════════╬═════════════════╬══════════╣
║        1 ║ PK_T1      ║ CLUSTERED       ║ FK_T2_T1 ║
║        2 ║ IX_T1_Id   ║ NONCLUSTERED    ║ NULL     ║
╚══════════╩════════════╩═════════════════╩══════════╝




 ALTER TABLE T2
    WITH NOCHECK 
    ADD CONSTRAINT [FK_T2_T1_NEW] FOREIGN KEY(T1_Id)
    REFERENCES T1(Id)

select
    ix.index_id,
    ix.name as index_name,
    ix.type_desc as index_type_desc,
    fk.name as fk_name
from sys.indexes ix
    left join sys.foreign_keys fk on
        fk.referenced_object_id = ix.object_id
        and fk.key_index_id = ix.index_id
        and fk.parent_object_id = object_id('T2')
where ix.object_id = object_id('T1');


╔══════════╦════════════╦═════════════════╦══════════════╗
║ index_id ║ index_name ║ index_type_desc ║   fk_name    ║
╠══════════╬════════════╬═════════════════╬══════════════╣
║        1 ║ PK_T1      ║ CLUSTERED       ║ FK_T2_T1     ║
║        2 ║ IX_T1_Id   ║ NONCLUSTERED    ║ FK_T2_T1_NEW ║
╚══════════╩════════════╩═════════════════╩══════════════╝   

ALTER TABLE T2  
DROP CONSTRAINT FK_T2_T1 

select
    ix.index_id,
    ix.name as index_name,
    ix.type_desc as index_type_desc,
    fk.name as fk_name
from sys.indexes ix
    left join sys.foreign_keys fk on
        fk.referenced_object_id = ix.object_id
        and fk.key_index_id = ix.index_id
        and fk.parent_object_id = object_id('T2')
where ix.object_id = object_id('T1');


╔══════════╦════════════╦═════════════════╦══════════════╗
║ index_id ║ index_name ║ index_type_desc ║   fk_name    ║
╠══════════╬════════════╬═════════════════╬══════════════╣
║        1 ║ PK_T1      ║ CLUSTERED       ║ NULL         ║
║        2 ║ IX_T1_Id   ║ NONCLUSTERED    ║ FK_T2_T1_NEW ║
╚══════════╩════════════╩═════════════════╩══════════════╝

看看是否可行，我正在尝试再添加一个FK，以便将新的FK链接到创建的新索引，并删除旧的FK。我知道问题不是要删除现有的问题，而是看看此选项是否对您有帮助。

另外，根据Max Vernon的评论：“ WITH NOCHECK选项将防止外键被优化程序信任。在某些时候，您必须更改外键，以便使用ALTER TABLE来信任外键...有检查”

该NOCHECK会只在创建的时候被忽略，但执行完整性contraint你在某个时间点运行此。