SQL服務器：存儲過程或函數

Question

我有2列（A as bool和B as text）的表，這些列可以是：

1. 兩者空
2. 如果A是假的，則B應爲空
3. 如果A爲真，則B應該是不爲空

有規則。我想要創建一個存儲過程或函數來在添加或更新行時（通過觸發器）檢查這些規則。什麼更好，存儲過程或函數？如果功能，哪種類型？一般來說，哪個變體是最好的（返回布爾值或其他方式等）？

Answer 1

我想你是在CHECK Constraint之後。

實施例：

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

我會用一個檢查約束有線到一個UDF。
下面是一個愚蠢的例子驗證，如果你插入一個人，他們的年齡將大於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 

這裏有一些「測試」：

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