Error handling with “THROW” command in SQL Server 2012
Error handling is one of the essential skill developer should have. It was very difficult to handle error efficiently till SQL Server 2000. After SQL Server 2000, we have get TRY…CATCH in SQL Server along with RAISERROR in SQL Server 2005. RAISERROR is even improved in form of “THROW” in SQL Server 2012.
Let us see how “THROW” command works for error handling efficiently in SQL Server 2012 because without know the error/bug in application, you can’t solve it. It is not possible/feasible, sometime, in big production environment to replicate same issue in development database, at the sametime, we can’t execute some command/query on live environment if it is affecting client’s data so efficient error handling is required so that you can log proper error along with its message, error number and other important things.
Let us create sample temporary table in AdventureWorks2012 database, if you don’t have Adventureworks2012 database with you, you can use your own database as I will be having temp table for this demonstration.
IF OBJECT_ID('tempdb..#TestingTHROWCommand') IS NOT NULL DROP TABLE #TestingTHROWCommand CREATE TABLE #TestingTHROWCommand ( ID INT IDENTITY(1,1) ,Name VARCHAR(50) ,OvertimeAmount INT ) INSERT INTO #TestingTHROWCommand SELECT 'Ritesh Shah',15 UNION ALL SELECT 'Teerth Shah',0 UNION ALL SELECT 'Rajan Jain',9 GO
Now let us try to execute one UPDATE statement where we will have one division operator which divide on “OvertimeAmount” field. We have value “0” with row number 2 so obviously we will be facing an error.
BEGIN TRY BEGIN TRANSACTION UPDATE #TestingTHROWCommand SET OvertimeAmount=95/OvertimeAmount COMMIT TRANSACTION END TRY BEGIN CATCH SELECT ERROR_NUMBER(),ERROR_MESSAGE(),ERROR_LINE() ROLLBACK TRANSACTION END CATCH GO
As soon as we will execute above code, we will be greeted with an error because on row # 2, we have 0 which will try to divide 95 and 0 can’t be used to divide anything. Here is the error message we will get:
(0 row(s) affected) 8134 Divide by zero error encountered. 3
Look at the error number, message and error line number given above. Now, we will try to handle error with different way as follow:
BEGIN TRY BEGIN TRANSACTION UPDATE #TestingTHROWCommand SET OvertimeAmount=95/OvertimeAmount COMMIT TRANSACTION END TRY BEGIN CATCH DECLARE @ErrorMsg NVARCHAR(MAX) = ERROR_MESSAGE() ROLLBACK TRANSACTION RAISERROR(@ErrorMsg,16,1) END CATCH GO
We have same UPDATE statement so obviously we will be getting error message again but this time, it will come by “RAISERROR” command. Here is the output of RAISERROR.
(0 row(s) affected) Msg 50000, Level 16, State 1, Line 10 Divide by zero error encountered.
Look at the error number and error line. It seems wrong because of “RAISERROR”. Let us now try to handle the error with “THROW” command.
BEGIN TRY BEGIN TRANSACTION UPDATE #TestingTHROWCommand SET OvertimeAmount=95/OvertimeAmount COMMIT TRANSACTION END TRY BEGIN CATCH ROLLBACK TRANSACTION; THROW END CATCH GO
we will again receive proper error message, number and line with “THROW” command. Have a look:
(0 row(s) affected) Msg 8134, Level 16, State 1, Line 3 Divide by zero error encountered.
I have recently seen many of the developer who are using SQL Server 2012, still uses “RAISERROR” as against “THROW”. I would highly recommend start using “THROW” command.
Reference: Ritesh Shah
Note: Microsoft Books online is a default reference of all articles.