SQL Server 2005 中使用 Try Catch 处理异常

TRY...CATCH是Sql Server 2005/2008令人印象深刻的新特性.提高了开发人员异常处理能力.没有理由不尝试一下Try.. Catch功能.

* TRY 块 - 包含可能产生异常的代码或脚本
* CATCH 块 - 如果TRY块出现异常,代码处理流将被路由到CATCH块.在这里你可以处理异常,记录日志等.
Sql Server中的Try Catch和C#,JAVA等语言的处理方式一脉相承.这种一致性才是最大的创新之处.

一、SQL SERVER 2000中异常处理

CREATE PROC usp_AccountTransaction 
 
  @AccountNum INT, 
 
  @Amount DECIMAL 
 
AS 
 
BEGIN 
 
  BEGIN TRANSACTION --beginning a transaction.. 
 
    UPDATE MyChecking SET Amount = Amount - @Amount 
 
      WHERE AccountNum = @AccountNum 
 
    IF @@ERROR != 0 --check @@ERROR variable after each DML statements.. 
 
    BEGIN 
 
      ROLLBACK TRANSACTION --RollBack Transaction if Error.. 
 
      RETURN 
 
    END 
 
    ELSE 
 
    BEGIN 
 
      UPDATE MySavings SET Amount = Amount + @Amount 
 
        WHERE AccountNum = @AccountNum 
 
      IF @@ERROR != 0 --check @@ERROR variable after each DML statements.. 
 
      BEGIN 
 
        ROLLBACK TRANSACTION --RollBack Transaction if Error.. 
 
        RETURN 
 
      END 
 
      ELSE 
 
      BEGIN 
 
        COMMIT TRANSACTION --finally, Commit the transaction if Success.. 
 
        RETURN 
 
      END 
 
    END 
 
END 
 
GO 

上面是Sql server 2000的一个存储过程,在每个数据库操作之后立即必须检查@@ERROR,进行Commit / RollBack该事务.
Sql server 2000中监测错误,只能通过监测全局遍历 @@ERROR.由于@@ERROR会被下一个数据库操作所覆盖. 所以在每次操作完后必须立即监测.

二、SQL SERVER 2005中异常处理

TRY...CATCH是SQL Server 2005提供的更具有可读性的语法.每个开发人员都熟悉这种写法.SQL Server 2005仍然支持@@ERROR这种用法.

1.try catch语法:

BEGIN TRY 
 
  Try Statement 1 
 
  Try Statement 2 
 
  ... 
 
  Try Statement M 
 
END TRY 
 
BEGIN CATCH 
 
  Catch Statement 1 
 
  Catch Statement 2 
 
  ... 
 
  Catch Statement N 
 
END CATCH 

2.获得错误信息的函数表:

下面系统函数在CATCH块有效.可以用来得到更多的错误信息:

函数 描述

ERROR_NUMBER() 返回导致运行 CATCH 块的错误消息的错误号。
ERROR_SEVERITY() 返回导致 CATCH 块运行的错误消息的严重级别
ERROR_STATE() 返回导致 CATCH 块运行的错误消息的状态号
ERROR_PROCEDURE() 返回出现错误的存储过程名称
ERROR_LINE() 返回发生错误的行号
ERROR_MESSAGE() 返回导致 CATCH 块运行的错误消息的完整文本

简单示例:

BEGIN TRY 
 
  SELECT GETDATE() 
 
  SELECT 1/0--Evergreen divide by zero example! 
 
END TRY 
 
BEGIN CATCH 
 
  SELECT 'There was an error! ' + ERROR_MESSAGE() 
 
  RETURN 
 
END CATCH; 

3.try catch回滚/提交事务的示例

ALTER PROC usp_AccountTransaction 
 
  @AccountNum INT, 
 
  @Amount DECIMAL 
 
AS 
 
BEGIN 
 
  BEGIN TRY --Start the Try Block.. 
 
    BEGIN TRANSACTION -- Start the transaction.. 
 
      UPDATE MyChecking SET Amount = Amount - @Amount 
 
        WHERE AccountNum = @AccountNum 
 
      UPDATE MySavings SET Amount = Amount + @Amount 
 
        WHERE AccountNum = @AccountNum 
 
    COMMIT TRAN -- Transaction Success! 
 
  END TRY 
 
  BEGIN CATCH 
 
    IF @@TRANCOUNT > 0 
 
      ROLLBACK TRAN --RollBack in case of Error 
 
    -- you can Raise ERROR with RAISEERROR() Statement including the details of the exception 
 
    RAISERROR(ERROR_MESSAGE(), ERROR_SEVERITY(), 1) 
 
  END CATCH 
 
END 
 
GO

三、实例讲解

创建错误日志表:

CREATE TABLE ErrorLog(errNum INT,ErrSev NVARCHAR(1000),ErrState INT,ErrProc NVARCHAR(1000),ErrLine INT, ErrMsg NVARCHAR(2000))

创建错误日志记录存储过程:

CREATE PROCEDURE ErrorLog
AS 
   SELECT ERROR_NUMBER() AS ErrNum,ERROR_SEVERITY()AS ErrSev,ERROR_STATE() AS ErrState,ERROR_PROCEDURE() AS ErrProc,ERROR_LINE()AS ErrLine,ERROR_MESSAGE()AS ErrMsg 
   INSERT 
   INTO ErrorLog 
   VALUES(ERROR_NUMBER(),ERROR_SEVERITY(),ERROR_STATE(),ERROR_PROCEDURE(),ERROR_LINE(),ERROR_MESSAGE())
GO

写一个存储过程吧!里面使用一下Try Catch:

USE [Your_Test]
GO
/****** Object: StoredProcedure [dbo].[getTodayBirthday]  
    Script Date: 05/17/2010 15:38:46 
    Author:jinho
    Desc:获取当天生日的所有人
    ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[getTodayBirthday]
AS
BEGIN TRY
 declare @today datetime; 
 SET @today = GETDATE();--获取今天的日期
 DECLARE @day VARCHAR(2);
 SET @day =REPLACE(DAY(@today),0,'');
 DECLARE @month VARCHAR(2) ;
 SET @month = REPLACE(month(@today),0,'');
 DECLARE @year VARCHAR(4);
 SET @year = YEAR(@today);
 SELECT * FROM dbo.UserInfo WHERE REPLACE(DAY(CONVERT(DATETIME,Birthday )),0,'') =@day AND REPLACE(MONTH(CONVERT(DATETIME,Brithday)),0,'')=@month AND Birthday IS NOT NULL 

 END TRY
 BEGIN CATCH
 ErrorLog --调用上面的存储过程,保存错误日志
 END CATCH

说明:ERROR_NUMBER(),ERROR_SEVERITY(),ERROR_STATE(),ERROR_PROCEDURE(),ERROR_LINE(),ERROR_MESSAGE() 这几个函数只能用在Catch里面!