@@ERROR (Transact-SQL)

Artykuł
12/08/2014

Returns the error number for the last Transact-SQL statement executed.

Ikona łącza do tematu Transact-SQL Syntax Conventions

Składnia

@@ERROR

Return Types

integer

Uwagi

Returns 0 if the previous Transact-SQL statement encountered no errors.

Returns an error number if the previous statement encountered an error. If the error was one of the errors in the sys.messages catalog view, then @@ERROR contains the value from the sys.messages.message_id column for that error. You can view the text associated with an @@ERROR error number in sys.messages.

Because @@ERROR is cleared and reset on each statement executed, check it immediately following the statement being verified, or save it to a local variable that can be checked later.

Use the TRY...CATCH construct to handle errors. The TRY...CATCH construct also supports additional system functions (ERROR_LINE, ERROR_MESSAGE, ERROR_PROCEDURE, ERROR_SEVERITY, and ERROR_STATE) that return more error information than @@ERROR. TRY...CATCH also supports an ERROR_NUMBER function that is not limited to returning the error number in the statement immediately after the statement that generated an error. For more information, see TRY...CATCH (Transact-SQL).

Examples

A. Using @@ERROR to detect a specific error

The following example uses @@ERROR to check for a check constraint violation (error #547) in an UPDATE statement.

USE AdventureWorks2012;
GO
UPDATE HumanResources.EmployeePayHistory
    SET PayFrequency = 4
    WHERE BusinessEntityID = 1;
IF @@ERROR = 547
    PRINT N'A check constraint violation occurred.';
GO

B. Using @@ERROR to conditionally exit a procedure

The following examples uses IF...ELSE statements to test @@ERROR after an INSERT statement in a stored procedure. The value of the @@ERROR variable determines the return code sent to the calling program, indicating success or failure of the procedure.

USE AdventureWorks2012;
GO
-- Drop the procedure if it already exists.
IF OBJECT_ID(N'HumanResources.usp_DeleteCandidate', N'P') IS NOT NULL
    DROP PROCEDURE HumanResources.usp_DeleteCandidate;
GO
-- Create the procedure.
CREATE PROCEDURE HumanResources.usp_DeleteCandidate 
    (
    @CandidateID INT
    )
AS
-- Execute the DELETE statement.
DELETE FROM HumanResources.JobCandidate
    WHERE JobCandidateID = @CandidateID;
-- Test the error value.
IF @@ERROR <> 0 
    BEGIN
        -- Return 99 to the calling program to indicate failure.
        PRINT N'An error occurred deleting the candidate information.';
        RETURN 99;
    END
ELSE
    BEGIN
        -- Return 0 to the calling program to indicate success.
        PRINT N'The job candidate has been deleted.';
        RETURN 0;
    END;
GO

C. Using @@ERROR with @@ROWCOUNT

The following example uses @@ERROR with @@ROWCOUNT to validate the operation of an UPDATE statement. The value of @@ERROR is checked for any indication of an error, and @@ROWCOUNT is used to ensure that the update was successfully applied to a row in the table.

USE AdventureWorks2012;
GO
IF OBJECT_ID(N'Purchasing.usp_ChangePurchaseOrderHeader',N'P')IS NOT NULL
    DROP PROCEDURE Purchasing.usp_ChangePurchaseOrderHeader;
GO
CREATE PROCEDURE Purchasing.usp_ChangePurchaseOrderHeader
    (
    @PurchaseOrderID INT
    ,@BusinessEntityID INT
   )
AS
-- Declare variables used in error checking.
DECLARE @ErrorVar INT;
DECLARE @RowCountVar INT;

-- Execute the UPDATE statement.
UPDATE PurchaseOrderHeader 
    SET BusinessEntityID = @BusinessEntityID 
    WHERE PurchaseOrderID = @PurchaseOrderID;

-- Save the @@ERROR and @@ROWCOUNT values in local 
-- variables before they are cleared.
SELECT @ErrorVar = @@ERROR
    ,@RowCountVar = @@ROWCOUNT;

-- Check for errors. If an invalid @BusinessEntityID was specified,
-- the UPDATE statement returns a foreign key violation error #547.
IF @ErrorVar <> 0
    BEGIN
        IF @ErrorVar = 547
            BEGIN
                PRINT N'ERROR: Invalid ID specified for new employee.';
                 RETURN 1;
            END
        ELSE
            BEGIN
                PRINT N'ERROR: error '
                    + RTRIM(CAST(@ErrorVar AS NVARCHAR(10)))
                    + N' occurred.';
                RETURN 2;
            END
    END

-- Check the row count. @RowCountVar is set to 0 
-- if an invalid @PurchaseOrderID was specified.
IF @RowCountVar = 0
    BEGIN
        PRINT 'Warning: The BusinessEntityID specified is not valid';
        RETURN 1;
    END
ELSE
    BEGIN
        PRINT 'Purchase order updated with the new employee';
        RETURN 0;
    END;
GO