Question

我有一个包含2列（A as bool和B as text）的表格，这些列可以是：

都是null
如果A为假，则B应为空
如果A为True，则B不应为空

有规则。我想创建一个存储过程或函数来在行添加或更新（通过触发器）时检查这些规则。什么是更好的，存储过程或功能？如果功能，哪种类型？一般来说，哪种变体是最好的（返回布尔或其他方式等）？

Answer 1

我认为你是在CHECK Constraint之后。

示例：

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

我会使用连接到UDF的CHECK CONSTRAINT 这是一个愚蠢的例子，证明如果你插入一个人，他们的年龄将大于17岁。

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

以下是一些＆＃34;测试＆＃34;：

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

SQL Server：存储过程或函数

2 个答案: