SQL : can't get IDENTITY value in Trigger

Question

我是 SQL 新手。我正在创建一个虚拟项目。在我的项目中，我有一个注册页面，我想创建一个用户名(名字 + 姓氏 + 用户 ID)。但问题是，我无法捕获用户 ID value.我已经使用了After Trigger和Instead Of Trigeer。下面是我的脚本 -

表格-

CREATE TABLE UserInfo
(
    UserID INT IDENTITY(1,1),
    FirstName NVARCHAR(500),
    LastName NVARCHAR(500),
    [Password] NVARCHAR(200),
    EmailID NVARCHAR(200),
    [Address] NVARCHAR(500),
    CountryID INT,
    StateID INT,
    UserName NVARCHAR(500)
)

插入数据过程 -

CREATE PROC Create_User    
 @FirstName NVARCHAR(500),    
 @LastName NVARCHAR(500),    
 @Password NVARCHAR(200),    
 @EmailID NVARCHAR(200),    
 @Address NVARCHAR(500),    
 @CountryID INT,    
 @StateID INT,    
 @UserID INT OUTPUT    
AS    
 BEGIN    
 INSERT INTO UserInfo (FirstName,LastName,[Password],EmailID,[Address],CountryID,StateID)    
 VALUES    
 (@FirstName,@LastName,@Password,@EmailID,@Address,@CountryID,@StateID)    

 SET @UserID = SCOPE_IDENTITY();    

 END 

触发后 -

CREATE TRIGGER Create_UserName
ON UserInfo
AFTER INSERT
AS
BEGIN
DECLARE @_UName VARCHAR(200);
SET @_UName = (SELECT FirstName+LastName+Cast(UserID AS NVARCHAR(100)) from INSERTED )

INSERT INTO UserInfo (UserName) VALUES (@_UName)
END
    GO

输出 - 插入两行

代替触发器 -

CREATE TRIGGER Create_UserName
ON UserInfo
INSTEAD OF INSERT
AS
BEGIN
DECLARE @UName NVARCHAR(200);
DECLARE @FName NVARCHAR(200);
DECLARE @LName NVARCHAR(200);
DECLARE @UPassword NVARCHAR(200);
DECLARE @UEmailID NVARCHAR(200);
DECLARE @UAddress NVARCHAR(200);
DECLARE @UCountryID INT;
DECLARE @UStateID INT;
SET @UName = (SELECT FirstName+LastName+Cast(UserID AS NVARCHAR(100)) from INSERTED )
SET @FName = (SELECT FirstName from INSERTED )
SET @LName = (SELECT LastName from INSERTED )
SET @UPassword = (SELECT [Password] from INSERTED )
SET @UEmailID = (SELECT EmailID from INSERTED )
SET @UAddress = (SELECT [Address] from INSERTED )
SET @UCountryID = (SELECT CountryID from INSERTED )
SET @UStateID = (SELECT StateID from INSERTED )




INSERT INTO UserInfo (FirstName,LastName,[Password],EmailID,[Address],CountryID,StateID,UserName)  
VALUES (@FName,@LName,@UPassword,@UEmailID,@UAddress,@UCountryID,@UStateID,@UName)
END
    GO

输出 - 这工作正常，但身份为 0。

请告诉我该怎么做？

提前致谢。

Answer 1

你有问题

• 为什么你有一个存储过程而不是？使用存储过程或替代触发器:不能同时使用
• 其次，触发器仅针对一行进行编码
• 后触发器正在插入新行，应该是更新

至于原因:

存储过程没有 INSERT 来捕获 IDENTITY 值:INSERT 的范围实际上是代替触发器。如果您切换到@@IDENTITY(不好的做法)，您将从 AFTER 触发器中获取 IDENTITY 值。

要做什么:

• 删除这两个触发器:它们不会增加任何值(value)

• 如果用户名无法更改，则向表中添加计算列

例如

ALTER TABLE UserInfo ADD UserName AS FirstName+LastName+Cast(UserID AS NVARCHAR(100)

• ...或者向存储过程添加更新，用户名稍后可以更改

例如

CREATE PROC Create_User    
...
AS    

SET NOCOUNT, XACT_ABORT ON

BEGIN TRY
 BEGIN TRAN

 INSERT INTO UserInfo
   (FirstName,LastName,[Password],EmailID,[Address],CountryID,StateID)    
 VALUES    
   (@FirstName,@LastName,@Password,@EmailID,@Address,@CountryID,@StateID)

 SET @UserID = SCOPE_IDENTITY();    

 UPDATE UserInfo
 SET UserName = @FirstName+@LastName+Cast@UserID AS NVARCHAR(100)
 WHERE UserID = @UserID

   COMMIT TRAN
END TRY
BEGIN CATCH
   IF XACT_STATE() <> 0 ROLLBACK TRAN
END CATCH
GO