SQL服务器：存储过程或函数

Question

我有2列（A as bool和B as text）的表，这些列可以是：

1. 两者空
2. 如果A是假的，则B应为空
3. 如果A为真，则B应该是不为空

有规则。我想要创建一个存储过程或函数来在添加或更新行时（通过触发器）检查这些规则。什么更好，存储过程或函数？如果功能，哪种类型？一般来说，哪个变体是最好的（返回布尔值或其他方式等）？

Answer 1

我想你是在CHECK Constraint之后。

实施例：

ALTER TABLE Xxx 
    ADD CONSTRAINT chk_Xxx 
    CHECK ((A IS NULL AND B IS NULL) 
     OR (A = 0 AND B IS NULL) 
     OR (A = 1 AND B IS NOT NULL) 
     ) ; 

Answer 2

我会用一个检查约束有线到一个UDF。
下面是一个愚蠢的例子验证，如果你插入一个人，他们的年龄将大于17

if NOT exists (select * from sysobjects 
    where id = object_id('dbo.udfOlderThan17Check') and sysstat & 0xf = 0) 
    BEGIN 
     print 'Creating the stubbed version of dbo.udfOlderThan17Check' 
     EXEC ('CREATE FUNCTION dbo.udfOlderThan17Check (@j as smallint) RETURNS bit AS BEGIN RETURN 0 END') 
    END 
GO 


ALTER FUNCTION dbo.udfOlderThan17Check (@Age smallint ) 
    RETURNS bit AS 
    BEGIN 
     declare @exists int 

     select @exists = 0 

     if (@Age IS NULL) 
      BEGIN 
       select @exists = 1 -- NULL VALUES SHOULD NOT BLOW UP THE CONSTRAINT CHECK 
      END 

     if (@exists = 0) 

     BEGIN 

      if @Age > 17 
       begin 
        select @exists = 1 
       end  

      END 

     return @exists 
    END 



GO 



IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = object_id(N'[dbo].[Person]') and OBJECTPROPERTY(id, N'IsUserTable') = 1) 
    BEGIN 
     DROP TABLE [dbo].[Person] 
    END 
GO 


CREATE TABLE [dbo].[Person] 
(
     PersonUUID [UNIQUEIDENTIFIER] NOT NULL DEFAULT NEWSEQUENTIALID() 
    , Age smallint not null 
) 

GO 


ALTER TABLE dbo.Person ADD CONSTRAINT PK_Person 
PRIMARY KEY NONCLUSTERED (PersonUUID) 
GO 


ALTER TABLE dbo.Person 
ADD CONSTRAINT [CK_Person_AgeValue] CHECK ([dbo].[udfOlderThan17Check]([Age]) != 0) 
GO 

这里有一些“测试”：

INSERT INTO dbo.Person (Age) values (33) 
INSERT INTO dbo.Person (Age) values (16) 

INSERT INTO dbo.Person (Age) select 333 UNION select 58 
INSERT INTO dbo.Person (Age) select 444 UNION select 4 

select * from dbo.Person