1.异常处理的语法：
引用
BEGIN TRY
{ sql_statement | statement_block }
END TRY
BEGIN CATCH
[ { sql_statement | statement_block } ]
END CATCH
我们将可能会出错的sql 写在begin try...end try 之间，若出错，刚程序就跳到紧接着的begin try...end try 的beign catch...end catch中，执行beign catch...end catch错误处理SQL。try..catch 是可以嵌套的。
2.系统提供的异常处理函数
引用
In the scope of a CATCH block, the following system functions can be used to obtain information about the error that caused the CATCH block to be executed:
ERROR_NUMBER() returns the number of the error.
ERROR_SEVERITY() returns the severity.
ERROR_STATE() returns the error state number.
ERROR_PROCEDURE() returns the name of the stored procedure or trigger where the error occurred.
ERROR_LINE() returns the line number inside the routine that caused the error.
ERROR_MESSAGE() returns the complete text of the error message. The text includes the values supplied for any substitutable parameters, such as lengths, object names, or times.
3.简单例子：
具体参考：http://msdn.microsoft.com/en-us/library/ms175976.aspx