exeption handling in sql

 BEGIN TRANSACTION
        BEGIN TRY
            -- Generate a Constraint violation Error.
            DELETE FROM IRCContactDetails
                    WHERE id = 6
        END TRY
        BEGIN CATCH
            SELECT
                    ERROR_NUMBER() AS ErrorNumber,
                    ERROR_SEVERITY() AS ErrorSeverity,
                    ERROR_STATE() AS ErrorState,
                    ERROR_MESSAGE() AS ErrorMessage

            IF @@TRANCOUNT > 0
                    ROLLBACK TRANSACTION;                   
        END CATCH;
       
        IF @@TRANCOUNT > 0
            COMMIT TRANSACTION;