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!
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