Introduction
Handling errors in SQL Server became easy with the number of different ways. SQL Server 2005 has introduced the new option that helps to handle the errors effectively. Sometimes we cannot capture the errors which occurred in the end user. Even if we want to know the errors which occurred in the end user, we need to write the code to send it to us. It creates an additional overhead for the server.
SQL Server 2005 introduced TRY
...CATCH
statement which helps us to handle the errors effectively in the back end. This handling of the exception can provide additional information about the errors.
TRY...CATCH
The TRY
...CATCH
statement works the same as in the programming languages. First it gets executed in the SQL statement which we have written in the TRY
block and if any error occurs, then it will get executed the CATCH
block.
BEGIN TRY
// SQL Statements
END TRY
BEGIN CATCH
//Handle the exception details
END CATCH
There are a number of error handling property statements like the following:
ERROR_NUMBER()
ERROR_STATE()
ERROR_SEVERITY()
ERROR_LINE()
ERROR_PROCEDURE()
ERROR_MESSAGE()
Normally, SQL Server stores the default error messages which occurred in the execution in the following system table:
select * from sys.messages
But we can create our own error message details with the help of this exception handling.
Handling the Exception using TRY...CATCH
The below example shows the practical implementation of TRY
...CATCH
exception handling technique in Northwind
database.
USE [NorthWind]
GO
IF OBJECT_ID('dbo.ErrorTracer') IS NOT NULL
BEGIN
DROP TABLE dbo.ErrorTracer
PRINT 'Table dbo.ErrorTracer Dropped'
END
GO
CREATE TABLE ErrorTracer
(
iErrorID INT PRIMARY KEY IDENTITY(1,1),
vErrorNumber INT,
vErrorState INT,
vErrorSeverity INT,
vErrorLine INT,
vErrorProc VARCHAR(MAX),
vErrorMsg VARCHAR(MAX),
vUserName VARCHAR(MAX),
vHostName VARCHAR(MAX),
dErrorDate DATETIME DEFAULT GETDATE()
)
IF OBJECT_ID('dbo.ErrorTracer') IS NOT NULL
BEGIN
PRINT 'Table dbo.ErrorTracer Created'
END
GO
IF OBJECT_ID('Proc_InsertErrorDetails') IS NOT NULL
BEGIN
DROP PROCEDURE [dbo].[Proc_InsertErrorDetails]
PRINT 'Procedure Proc_InsertErrorDetails Dropped'
END
GO
CREATE PROCEDURE Proc_InsertErrorDetails
AS
BEGIN
SET NOCOUNT ON
SET XACT_ABORT ON
DECLARE @ErrorNumber VARCHAR(MAX)
DECLARE @ErrorState VARCHAR(MAX)
DECLARE @ErrorSeverity VARCHAR(MAX)
DECLARE @ErrorLine VARCHAR(MAX)
DECLARE @ErrorProc VARCHAR(MAX)
DECLARE @ErrorMesg VARCHAR(MAX)
DECLARE @vUserName VARCHAR(MAX)
DECLARE @vHostName VARCHAR(MAX)
SELECT @ErrorNumber = ERROR_NUMBER()
,@ErrorState = ERROR_STATE()
,@ErrorSeverity = ERROR_SEVERITY()
,@ErrorLine = ERROR_LINE()
,@ErrorProc = ERROR_PROCEDURE()
,@ErrorMesg = ERROR_MESSAGE()
,@vUserName = SUSER_SNAME()
,@vHostName = Host_NAME()
INSERT INTO ErrorTracer(vErrorNumber,vErrorState,vErrorSeverity,vErrorLine,_
vErrorProc,vErrorMsg,vUserName,vHostName,dErrorDate)
VALUES(@ErrorNumber,@ErrorState,@ErrorSeverity,@ErrorLine,@ErrorProc,_
@ErrorMesg,@vUserName,@vHostName,GETDATE())
END
IF OBJECT_ID('Proc_InsertErrorDetails') IS NOT NULL
BEGIN
PRINT 'Procedure Proc_InsertErrorDetails Created'
END
GO
IF OBJECT_ID('Proc_ExceptionHandlingExample') IS NOT NULL
BEGIN
DROP PROCEDURE [dbo].[Proc_ExceptionHandlingExample]
PRINT 'Procedure Proc_ExceptionHandlingExample Dropped'
END
GO
CREATE PROCEDURE Proc_ExceptionHandlingExample
AS
BEGIN
SET NOCOUNT ON
SET XACT_ABORT ON
BEGIN TRY
SELECT 15/0
END TRY
BEGIN CATCH
EXEC Proc_InsertErrorDetails
END CATCH
END
IF OBJECT_ID('Proc_ExceptionHandlingExample') IS NOT NULL
BEGIN
PRINT 'Procedure Proc_ExceptionHandlingExample Created'
END
GO
EXEC Proc_ExceptionHandlingExample
SELECT * FROM ErrorTracer
Steps
Step 1: Create the custom error table with the name "ErrorTracer
".
Step 2: Write the common Stored procedures for handling the current exception in the name of Proc_InsertErrorDetails
which will help us to insert the error details into step1
created table.
Step 3: Write a sample procedure and execute with the exception handling using TRY
...CATCH
statement. Whenever an error occurs, it will call the Proc_InsertErrorDetails
and that will insert the error details.
Step 4: Now, check the ErrorTracer
table that will list out the captured error details.
Conclusion
This customized error handling techniques help us to improve the back end error details effectively. We have given the date and username details in the table that will help you to find the error details based on the date and username respectively.
History
- 17th July, 2009: Initial post