是否有可能一个逻辑约束添加到外键？(Is it possible to add a logic Co

2019-06-24 00:58发布

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叼着烟拽天下

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我有两个表，我添加了一个外键约束。 KEWL - 伟大工程。现在，是有可能进一步限制对父表中的一些数据之间的关系？

基本上，我有父表的动物，并为子表wishto只包含在父数据....嗯..哺乳动物的数据。

例如。

Animals
^^^^^^^
AnimalId INT PK NOT NULL IDENTITY
AnimalType TINYINT NOT NULL -- 1: Mammal, 2:Reptile, etc..
Name

Mammals
^^^^^^^
AnimalId INT PK FK NOT NULL
NumberOfMammaryGlads TINYINT NOT NULL

所以，我wishto确保该AnimalId只能是类型Animals.AnimalType = 1

这可能吗？？

我不想让别人去尝试，并插入一些信息对爬行动物，在子表...

干杯:)

编辑：

我想我不得不使用检查约束（从我的前两个答案，下面证实- ！欢呼），但我不知道如何（如SQL语法指动物表）。

更新：

亚历克斯有一个非常好的职位（下文）基准测试一些建议....一个非常良好的阅读！

Answer 1:

我跑一个小的标杆 - 在这种情况下，用UDF的方式运行近100倍慢。

一个FK的CPU时间的开销= 375毫秒 - 297毫秒= 78毫秒

的UDF的CPU时间的开销= 7750毫秒 - 297毫秒= 7453毫秒

这里的SQL代码...

- 建立一个辅助表数与128K行：

CREATE TABLE dbo.Numbers(n INT NOT NULL PRIMARY KEY)
GO
DECLARE @i INT;
SET @i = 1;
INSERT INTO dbo.Numbers(n) SELECT 1;
WHILE @i<128000 BEGIN
  INSERT INTO dbo.Numbers(n)
    SELECT n + @i FROM dbo.Numbers;
  SET @i = @i * 2;
END;
GO

- 表

CREATE TABLE dbo.Animals
(AnimalId INT NOT NULL IDENTITY PRIMARY KEY,
AnimalType TINYINT NOT NULL, -- 1: Mammal, 2:Reptile, etc..
Name VARCHAR(30))
GO
ALTER TABLE dbo.Animals
ADD CONSTRAINT UNQ_Animals UNIQUE(AnimalId, AnimalType)
GO
CREATE FUNCTION dbo.GetAnimalType(@AnimalId INT)
RETURNS TINYINT
AS
BEGIN
DECLARE @ret TINYINT;
SELECT @ret = AnimalType FROM dbo.Animals
  WHERE AnimalId = @AnimalId;
RETURN @ret;
END
GO
CREATE TABLE dbo.Mammals
(AnimalId INT NOT NULL PRIMARY KEY,
SomeOtherStuff VARCHAR(10),
CONSTRAINT Chk_AnimalType_Mammal CHECK(dbo.GetAnimalType(AnimalId)=1)
);
GO

---与UDF填充：

INSERT INTO dbo.Animals
  (AnimalType, Name)
SELECT 1, 'some name' FROM dbo.Numbers;
GO
SET STATISTICS IO ON
SET STATISTICS TIME ON
GO
INSERT INTO dbo.Mammals
(AnimalId,SomeOtherStuff)
SELECT n, 'some info' FROM dbo.Numbers;

结果是：

SQL Server parse and compile time: 
CPU time = 0 ms, elapsed time = 2 ms.
Table 'Mammals'. Scan count 0, logical reads 272135, 
    physical reads 0, read-ahead reads 0, lob logical reads 0, 
    lob physical reads 0, lob read-ahead reads 0.
Table 'Numbers'. Scan count 1, logical reads 441, physical reads 0, 
    read-ahead reads 0, lob logical reads 0, lob physical reads 0, 
    lob read-ahead reads 0.

SQL Server Execution Times:
    CPU time = 7750 ms,  elapsed time = 7830 ms.

(131072 row(s) affected)

---与FK填充：

CREATE TABLE dbo.Mammals2
(AnimalId INT NOT NULL PRIMARY KEY,
AnimalType TINYINT NOT NULL,
SomeOtherStuff VARCHAR(10),
CONSTRAINT Chk_Mammals2_AnimalType_Mammal CHECK(AnimalType=1),
CONSTRAINT FK_Mammals_Animals FOREIGN KEY(AnimalId, AnimalType)
  REFERENCES dbo.Animals(AnimalId, AnimalType)
);

INSERT INTO dbo.Mammals2
(AnimalId,AnimalType,SomeOtherStuff)
SELECT n, 1, 'some info' FROM dbo.Numbers;

结果是：

SQL Server parse and compile time: 
   CPU time = 93 ms, elapsed time = 100 ms.
Table 'Animals'. Scan count 1, logical reads 132, physical reads 0,
    read-ahead reads 0, lob logical reads 0, lob physical reads 0, 
    lob read-ahead reads 0.
Table 'Mammals2'. Scan count 0, logical reads 275381, physical reads 0,
   read-ahead reads 0, lob logical reads 0, lob physical reads 0, 
   lob read-ahead reads 0.
Table 'Numbers'. Scan count 1, logical reads 441, physical reads 0,
   read-ahead reads 0, lob logical reads 0, lob physical reads 0, 
   lob read-ahead reads 0.

SQL Server Execution Times:
   CPU time = 375 ms,  elapsed time = 383 ms.

- 填充，没有任何的完整性：

CREATE TABLE dbo.Mammals3
(AnimalId INT NOT NULL PRIMARY KEY,
SomeOtherStuff VARCHAR(10)
);
INSERT INTO dbo.Mammals3
(AnimalId,SomeOtherStuff)
SELECT n,  'some info' FROM dbo.Numbers;

结果是：
SQL Server分析和编译时间：CPU时间= 1毫秒，经过的时间= 1毫秒。

SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 66 ms.
Table 'Mammals3'. Scan count 0, logical reads 272135, physical reads 0,
    read-ahead reads 0, lob logical reads 0, lob physical reads 0,
    lob read-ahead reads 0.
Table 'Numbers'. Scan count 1, logical reads 441, physical reads 0, 
    read-ahead reads 0, lob logical reads 0, lob physical reads 0, 
    lob read-ahead reads 0.

SQL Server Execution Times:
   CPU time = 297 ms,  elapsed time = 303 ms.

(131072 row(s) affected)

一个FK的CPU时间的开销= 375毫秒 - 297毫秒= 78毫秒
的UDF的CPU时间的开销= 7750毫秒 - 297毫秒= 7453毫秒

Answer 2:

对动物（AnimalId，AnimalType）添加AnimalType哺乳动物唯一约束，并且使用检查约束，以确保它始终为1。有一个FK指（AnimalId，AnimalType）。

Answer 3:

您可以创建在列检查约束。

ALTER TABLE Mammals
ADD CONSTRAINT CHK_AnimalType CHECK (dbo.fnGetAnimalType(animalId) = 1 );

现在你需要一个功能fnGetAnimalType将返回给定的animalId的animalType。

下面是更多的从MSDN信息。

Answer 4:

给予了有力的保证，你将需要两个检查约束去两种方式。如果你只限制Mammals有人可以更新Animals.AnimalType和不一致的状态获取数据。

Answer 5:

我想你想的哺乳动物表中使用检查约束。

http://msdn.microsoft.com/en-us/library/ms188258.aspx

Answer 6:

这听起来像表继承-我最近问了一个问题（不能链接，因为我太新了！），其答案铅寻找这种解决方案。

我与货币交易若交易是父表和交易类型，如支票，银行转帐，并且CC是子表工作。使用交易类型，外键约束和计算列查找表我是能够执行在每个子表的类型约束。

请查看文章的实施细则。

Answer 7:

下面是建立在“中讨论的技术中的另一种方法强制执行复杂的约束与索引视图 ”强制执行AnimalType约束。这种方法的优点是，它避免了在亚型表中的额外的列; 然而，它比呈现复合外键慢AlexKuznetsov的回答（虽然远不一样慢得可怜的UDF方法）。

我跑了同一系列的测试，AlexKuznetsov，但增加的行数从131,072 1,048,576。下面是结果的摘要：

-- No integrity check:                         2488 ms.
-- With composite foreign key:                 4404 ms.
-- With indexed view and unique index:         7063 ms. <- new
-- With check constraint calling scalar UDF:  78304 ms.

模式定义：

CREATE TABLE dbo.Mammals4
(
    AnimalId INT NOT NULL PRIMARY KEY
        REFERENCES dbo.Animals (AnimalId),
    SomeOtherStuff VARCHAR(10)
);

CREATE TABLE dbo.TwoRows   -- can be reused for other similar indexed views
(
    n TINYINT NOT NULL PRIMARY KEY
)

INSERT INTO dbo.TwoRows
VALUES (1), (2)

GO

CREATE VIEW dbo.CK_Mammals4 WITH SCHEMABINDING
AS
    SELECT M.AnimalId
    FROM dbo.Mammals4 M
        JOIN dbo.Animals A
            ON A.AnimalId = M.AnimalId
        CROSS JOIN dbo.TwoRows
    WHERE A.AnimalType != 1

GO

CREATE UNIQUE CLUSTERED INDEX CKIX_Mammals4
ON dbo.CK_Mammals4 (AnimalId)

检测方法与结果：

-- No integrity check:

INSERT INTO dbo.Mammals3 (AnimalId, SomeOtherStuff)
SELECT n, 'some info' FROM dbo.Numbers;

Table 'Mammals3'. Scan count 0, logical reads 2969171, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Numbers'. Scan count 1, logical reads 1724, physical reads 3, read-ahead reads 1720, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

 SQL Server Execution Times:
   CPU time = 2247 ms,  elapsed time = 2488 ms.

-- With composite foreign key:

INSERT INTO dbo.Mammals2 (AnimalId, AnimalType, SomeOtherStuff)
SELECT n, 1, 'some info' FROM dbo.Numbers;

Table 'Animals'. Scan count 1, logical reads 1432, physical reads 3, read-ahead reads 1428, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Mammals2'. Scan count 0, logical reads 3163291, physical reads 3, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Numbers'. Scan count 1, logical reads 1724, physical reads 3, read-ahead reads 1720, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

 SQL Server Execution Times:
   CPU time = 3822 ms,  elapsed time = 4404 ms.

-- With indexed view and unique index:

INSERT INTO dbo.Mammals4 (AnimalId, SomeOtherStuff)
SELECT n, 'some info' FROM dbo.Numbers

Table 'CK_Mammals4'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Animals'. Scan count 2, logical reads 4953, physical reads 6, read-ahead reads 4945, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Worktable'. Scan count 2, logical reads 2978842, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Mammals4'. Scan count 0, logical reads 3162616, physical reads 3, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Numbers'. Scan count 1, logical reads 1724, physical reads 3, read-ahead reads 1720, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

 SQL Server Execution Times:
   CPU time = 6209 ms,  elapsed time = 7063 ms.

-- With check constraint calling scalar UDF:

INSERT INTO dbo.Mammals (AnimalId, SomeOtherStuff)
SELECT n, 'some info' FROM dbo.Numbers;

Table 'Mammals'. Scan count 0, logical reads 2969171, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Numbers'. Scan count 1, logical reads 1724, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

 SQL Server Execution Times:
   CPU time = 77424 ms,  elapsed time = 78304 ms.

文章来源: Is it possible to add a logic Constraint to a Foreign Key?