SQL SERVER – 2005 – Explanation of TRY…CATCH and ERROR Handling

SQL Server 2005 offers a more robust set of tools for handling errors than in previous versions of SQL Server. Deadlocks, which are virtually impossible to handle at the database level in SQL Server 2000, can now be handled with ease. By taking advantage of these new features, you can focus more on IT business strategy development and less on what needs to happen when errors occur. In SQL Server 2005, @@ERROR variable is no longer needed after every statement executed, as was the case in SQL Server 2000. SQL Server 2005 provides the TRY…CATCH construct, which is already present in many modern programming languages. TRY/CATCH helps to write logic separate the action and error handling code. The code meant for the action is enclosed in the TRY block and the code for error handling is enclosed in the CATCH block. In case the code within the TRY block fails, the control automatically jumps to the CATCH block, letting the transaction roll back and resume execution. In addition to this, the CATCH block captures and provides error information that shows you the ID, message text, state, severity and transaction state of an error.

Functions to be used in CATCH block are :

  • ERROR_NUMBER: returns the error number, and is the same value of @@ERROR.
  • ERROR_SEVERITY: returns the severity level of the error that invoked the CATCH block.
  • ERROR_STATE: returns the state number of the error.
  • ERROR_LINE: returns the line number where the error occurred.
  • ERROR_PROCEDURE: returns the name of the stored procedure or trigger for which the error occurred.
  • ERROR_MESSAGE: returns the full message text of the error. The text includes the values supplied for any substitutable parameters, such as lengths, object names, or times.

You can use these functions anywhere inside a CATCH block, and they will return information regarding the error that has occurred. These functions will return the value null outside of the CATCH block.

Syntax:

BEGIN TRY
{ sql_statement |
statement_block }
END TRY
BEGIN CATCH
{ sql_statement |
statement_block }
END CATCH

The TRY or CATCH block can contain a single T-SQL statement or a series of statements. The CATCH block must follow immediately after the TRY block. The TRY/CATCH block cannot span more than a single batch. In addition, TRY/CATCH block cannot span an IF/ELSE statement.

Example of TRY…CATCH:

BEGIN TRY
DECLARE @X INT
---- Divide by zero to generate Error
SET @X = 1/0
PRINT 'Command after error in TRY block'
END TRY
BEGIN CATCH
PRINT 'Error Detected'
END CATCH
PRINT 'Command after TRY/CATCH blocks'

Above code will return following result:

Error Detected
Command after TRY/CATCH blocks


If all the statements within the TRY block are executed successfully, then processing does not enter the CATCH block, but instead skips over the CATCH block and executes the first statement following the END CATCH statement. Removing SET statement in above code PRINT ‘Error Detected’ statement is not executed, but the PRINT statement within the TRY block is executed, as well as the PRINT statement after the TRY/CATCH block. TRY/CATCH blocks can be nested.

Limitation of TRY…CATCH:

  • Compiled errors are not caught.
  • Deferred name resolution errors created by statement level recompilations. (If process is terminated by Kill commands or broken client connections TRY…CATCH will be not effective)
  • Errors with a severity greater than 10 that do not terminate their database connection are caught in the TRY/CATCH block.

For errors that are not trapped, SQL Server 2005 passes control back to the application immediately, without executing any CATCH block code.

Similar example of TRY…CATCH which includes all the ERROR functions:

USE AdventureWorks;
GO
BEGIN TRY
-- Generate a divide-by-zero error.
SELECT 1/0;
END TRY
BEGIN CATCH
SELECT
ERROR_NUMBER() AS ErrorNumber,
ERROR_SEVERITY() AS ErrorSeverity,
ERROR_STATE() AS ErrorState,
ERROR_PROCEDURE() AS ErrorProcedure,
ERROR_LINE() AS ErrorLine,
ERROR_MESSAGE() AS ErrorMessage;
END CATCH;
GO



Reference : Pinal Dave (https://blog.sqlauthority.com) , BOL

SQL Error Messages, SQL Scripts, SQL Server Security
Previous Post
SQL SERVER – 2005 – Silent Installation – Unattended Installation
Next Post
SQL SERVER – UDF – User Defined Function to Extract Only Numbers From String

Related Posts

47 Comments. Leave new

  • parveen kumar
    March 31, 2010 3:19 pm

    CAN WE USE TRY CATCH IN FUNCTIONS?

    Reply
  • Hi,

    I tried to insert data into a table which doesn’t exists from a SP. In this case, I am not able to trap the error in CATCH block and it breaks while running in between.

    BEGIN TRY
    –Insert statement
    END TRY
    BEGIN CATCH
    PRINT ‘Error Detected’
    END CATCH

    Output:
    Msg 208, Level 16, State 1, Procedure usp_Calculation, Line 805
    Invalid object name ‘tbl_Allocation_Debug’.

    Reply
  • Murugan Killada
    April 22, 2010 12:06 am

    Check upfront if object exists or not.

    If exists(
    Select * from information_schema.tables where table_name=
    ) … then go ahead inserting data.

    Reply
  • Hi ,

    kindly let me know how to capture the exception raised by the below sql and i want to use insert Try and Catch in the sql below.

    DECLARE @triprequest varchar (50)
    DECLARE @xml_str varchar(4000)
    DECLARE @hdoc int
    declare @temp_table_travel_Req_xml_det table ([triprequest] varchar (50),[name] varchar (50), [created_by] varchar (50), [action] varchar (16), [created_on] datetime)
    DECLARE xml_cur cursor for
    SELECT CMTRAVELCOMMENTS.tripRequest triprequest, cast(cast(CMTRAVELCOMMENTS.config as
    varbinary(8000)) as VARCHAR(8000)) xml_str
    FROM CMTRAVELCOMMENTS, PCMTRAVELREQUEST
    WHERE
    PCMTRAVELREQUEST.NODESTATE = ‘Approved request’
    and CMTRAVELCOMMENTS.tripRequest=PCMTRAVELREQUEST.tripRequest
    OPEN xml_cur
    FETCH xml_cur into @triprequest,@xml_str
    WHILE(@@fetch_status=0)
    BEGIN
    EXEC sp_xml_preparedocument @hdoc OUTPUT, @xml_str
    INSERT into temp_table_travel_Req_xml_det
    SELECT @triprequest,*
    FROM OPENXML (@hdoc,’/cm-comments/comments’, 3)
    WITH ([name] varchar (50), [created_by] varchar (50), [action] varchar (16), [created_on] datetime)
    EXEC sp_xml_removedocument @hdoc
    print @triprequest
    FETCH xml_cur into @triprequest,@xml_str
    END
    CLOSE xml_cur
    DEALLOCATE xml_cur

    Reply
  • Hello Sir,

    Is there any way to catch error with severity less than 10.
    I have a Stored Proc wherein dynamic sql query is generated. If the query is wrong, How can i catch the exception?

    If the query generated can be wrong, than the user input is wrong and hence i need to update another table.

    Can u pls help ..

    Thanks
    Geervani

    Reply
  • Is it possible for try..catch to be global for some reason? We are seeing stored procedures calling an error statement even though there is no error checking (try catch or otherwise) on that particular statement. For example, in the sp we might do inserts and on those we check @@error and we always do an insert into table called errors if we see a failure, but we have some update statements that we expect to not find anything to update in certain conditions so we do not check for any errors yet when they do not work we are getting an error on not being able to insert into the table errors and the sp bombs. Is it possible for there to be a global try catch that gets called somehow?

    Reply
  • Mark Freeman
    June 8, 2010 12:51 am

    I have a stored procedure that updates a linked server. The linked server is returning an error (because the update would violate a business rule).

    ERROR_MESSAGE() has ‘Cannot fetch a row from OLE DB provider “” for linked server “”.’

    This is OK as far as it goes. But when I debug this in VS 2008, the Debug Window displays this much more detailed info:

    OLE DB provider “” for linked server “” returned message “Cursor fetch row failed.
    exception 98
    VER2021-Service Records can not overlap for DSP.”.

    How can I access that more detailed message within my stored procedure’s CATCH block?

    Reply
  • Prashant Goyal
    July 30, 2010 11:56 am

    i want to know in sql script what type of
    exception are generate like FOREGIN KEY,PRIMARY KEY, UNIQUE KEY VIOLATION
    so that i take a step to generate a appropriate message to
    user that it understand what is error.

    Reply
  • Sandipak Bagchi
    September 24, 2010 2:59 am

    Pinal,

    Can you please provide some more info on NESTED TRY CATCH blocks and how the control passes from one to another during calling one stored procedure from another.

    I have the following situation

    CREATE PROCEDURE sp_a(
    ….)
    AS
    BEGIN…
    ..
    BEGIN TRY — Outer Try block
    UPDATE TABLE a…..WHERE …

    EXEC sp_b

    UPDATE TABLE….
    SET a…..
    WHERE….

    END TRY
    BEGIN CATCH

    SET @ErrorMsg = ‘ErrNo: ‘ + ERROR_NUMBER() + ‘ Msg: ‘ +
    ERROR_MESSAGE()

    END CATCH

    END

    —- End of Stored Proc – sp_a

    CREATE PROCEDURE sp_b(..
    …)

    BEGIN TRY — Nested Try Block – Inner block
    INSERT INTO TABLE…..
    VALUES(…)
    END TRY
    BEGIN CATCH

    SET @ErrorMsg = ‘ErrNo: ‘ + ERROR_NUMBER() + ‘ Msg: ‘ +
    ERROR_MESSAGE()
    END CATCH

    END —

    —- End of Stored Proc sp_b

    So in this case if the sproc sp_b returns error, does the stored procedure capture that error and goes to the Outer CATCH block or do I have log the Inner CATCH error separately into a table.

    Any feedback would be much appreciated

    Reply
  • I understand the Try Catch, but how can I catch that the link server is down, and test it without taking down the link server?

    BEGIN TRY

    –SELECT 1/0
    SELECT state_desc FROM LinkedServerName.master.sys.databases WHERE [Name] = ‘DBaseName’

    END TRY
    BEGIN CATCH

    SELECT
    ERROR_NUMBER() AS ErrorNumber,
    ERROR_SEVERITY() AS ErrorSeverity,
    ERROR_STATE() AS ErrorState,
    ERROR_PROCEDURE() AS ErrorProcedure,
    ERROR_LINE() AS ErrorLine,
    ERROR_MESSAGE() AS ErrorMessage;

    END CATCH

    Reply
  • Shaik Nazeer Hussain
    July 20, 2011 4:15 pm

    Hi,

    I am using sqlserver 2005.if i execute following lines of code in sqlserver catch bolck not executing.Since i dont have Permanenttable and Temporarytable in my db.

    BEGIN TRY
    insert Permanenttable
    select * from Temporarytable
    END TRY
    BEGIN CATCH
    print ‘catch fired’
    END CATCH

    Reply
  • Shaik Nazeer Hussain
    July 21, 2011 10:52 am

    I understand try catch blocks having some limitation.
    But how can i handle this type of exception?
    I am having scenario like following

    Create procedure sp1
    as
    Begin

    Begin Try
    Begin Tran

    Declare cursor1 cursor for …………
    ………………
    While @@Fetch_status=0
    Begin

    Declare cursor2 cursor for …………
    ………………
    While @@Fetch_status=0
    Begin

    Declare cursor3 cursor for …………
    ………………
    While @@Fetch_status=0
    Begin

    insert Permanenttable
    select * from Temporarytable
    End
    End

    End

    IF @@TRANCOUNT > 0
    COMMIT TRAN
    End Try

    Begin catch

    Rollback tran

    IF CURSOR_STATUS(‘GLOBAL’, ‘Cursor1’) >= 0
    BEGIN
    CLOSE Cursor1
    DEALLOCATE Cursor1
    END
    IF CURSOR_STATUS(‘GLOBAL’, ‘Cursor2’) >= 0
    BEGIN
    CLOSE Cursor2
    DEALLOCATE Cursor2
    END

    IF CURSOR_STATUS(‘GLOBAL’, ‘Cursor3’) >= 0
    BEGIN
    CLOSE Cursor3
    DEALLOCATE Cursor3
    END
    End catch

    END

    If exception raised at the time of inserting then it will terminate.But my all cursors will be open state only.

    If next time i execute this SP it will give Cursor1 already exist and transaction opened error.

    So can any one tell me how can i acheive this type of scenario.

    Reply
  • ALTER PROC SAMPLE1
    AS
    BEGIN
    BEGIN TRY
    PRINT ‘1’
    DECLARE @SQL VARCHAR(MAX)
    SET @SQL = ‘insert Permanenttable select * from Temporarytable’
    EXEC(@SQL)
    — select 1/0
    PRINT ‘2’
    END TRY
    BEGIN CATCH
    print ‘catch fired’
    SELECT
    ERROR_NUMBER() AS ErrorNumber,
    ERROR_SEVERITY() AS ErrorSeverity,
    ERROR_STATE() as ErrorState,
    ERROR_PROCEDURE() as ErrorProcedure,
    ERROR_LINE() as ErrorLine,
    ERROR_MESSAGE() as ErrorMessage;
    END CATCH
    END

    Reply
  • which one we should use transaction/@@error or try/catch.

    Reply
  • MyDoggieJessie
    November 18, 2011 3:07 am

    The best way to test for a linked server is to use SQL’s built in system procedure:

    Ex: EXEC sys.sp_testlinkedserver ‘yourlinkedserver’

    Reply
  • can we write insert statement in a trigger catch block in sql server 2005

    Reply
  • Hi….. Pinal

    i m new to sql server, so i wanted to know that how can i return the error code using error_number() and error message using error_message() with variable to the calling…………. like we can return in oracle using sqlcode, sqlerrm

    Reply
  • Hi… Pinal

    I have been following your blog and failed to understand why the stored procedure gets printed “NULL” when it goes to catch. It is returning the stored procedure name only when there is foreign key relationship violation. or else every time it is “NULL” Could you please help me .

    Reply
  • Karan Mistry
    May 15, 2013 5:52 pm

    Thanks… was simple in understanding

    Reply
  • sushil bhati
    June 23, 2016 2:31 pm

    can we use finally block with try catch in sql server any version.if we not use so why we not use.

    Reply

Leave a Reply

Menu
Exit mobile version