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Posts Tagged ‘T-SQL’

Catch ‘n Throw Errors in SQL Server “Denali”

May 6, 2011 Leave a comment

SQL Server “Denali” adds a new feature in Error Handling called “THROW”

Current version already has RAISERROR, which you can already use to raise Error from your procedures, then why do we need this new “THROW” option,

Let us see the differences

/* RAISERROR */

BEGIN TRY 
    SELECT 1/0 
END TRY 
BEGIN CATCH 
    
    DECLARE @ERRORNUMBER INT = ERROR_NUMBER() 
    DECLARE @ERRORMESSAGE VARCHAR(500) = ERROR_MESSAGE() 
    
    SELECT @ERRORNUMBER, @ERRORMESSAGE

    RAISERROR(@ERRORNUMBER, 16, -1) 
END CATCH

In the above code, we are creating Divide by Zero error in the Try Block and then Catching that Error in Catch Block and Display the Error details and then need to return the same error to calling application

Output from SELECT:

image

Msg 2732, Level 16, State 1, Line 11 Error number 8134 is invalid. The number must be from 13000 through 2147483647 and it cannot be 50000.

RAISERROR(@ERRORNUMBER, 16, –1) causes the above error instead of returning that error to application

See the same implementation using THROW and how it works

/* THROW Demo */

BEGIN TRY 
    SELECT 1/0 
END TRY 
BEGIN CATCH 
    PRINT 'Error Number: ' + CAST(ERROR_NUMBER() AS VARCHAR);
    PRINT 'Error Line: ' + CAST(ERROR_LINE() AS VARCHAR);

    THROW;
END CATCH 
(0 row(s) affected)
Error Number: 8134
Error Line: 5
Msg 8134, Level 16, State 1, Line 5
Divide by zero error encountered.

 

The Error number and Error Line was printed and then the same error was thrown back to calling application

You can use THROW to log errors in CATCH block and return the same error back to calling application easily.

Server Side Paging simplified in SQL Server “Denali”

May 5, 2011 Leave a comment

SQL Server “Denali” is the new upcoming version of SQL Server, it has numerous new features

Let us review the new built-in Paging feature “FETCH FIRST”, “FETCH NEXT”

–How to Fetch 1st Page of 10 Rows

USE [AdventureWorks2008R2]
GO

DECLARE @PageNumber INT = 1
DECLARE @PageSize INT = 10

SELECT [ProductID],[Name],[ProductNumber],[MakeFlag],[FinishedGoodsFlag],[Color],[StandardCost],[ListPrice]
  FROM [Production].[Product]
  ORDER BY [Name]
  OFFSET (@PageNumber * @PageSize) – @PageSize ROWS
  FETCH FIRST @PageSize ROWS ONLY

–How to Fetch 2nd Page of 10 Rows

SET @PageNumber = 2

SELECT [ProductID],[Name],[ProductNumber],[MakeFlag],[FinishedGoodsFlag],[Color],[StandardCost],[ListPrice]
  FROM [Production].[Product]
  ORDER BY [Name]
  OFFSET (@PageNumber * @PageSize) – @PageSize ROWS
  FETCH NEXT @PageSize ROWS ONLY;

— How to Fetch all records skipping first 100 Records

SELECT [ProductID],[Name],[ProductNumber],[MakeFlag],[FinishedGoodsFlag],[Color],[StandardCost],[ListPrice]
  FROM [Production].[Product]
  ORDER BY [Name]
  OFFSET 100 ROWs

— How to implement Customizable Paging support using the new feature

–Create a Personalization table to store PageSettings

CREATE TABLE PageSettings
(
    LoggedInUserName    VARCHAR(128),
    PageSize        Int
)

–Add some Page setting Records

INSERT INTO PageSettings (LoggedInUserName, PageSize) Values (‘bill’,10)
INSERT INTO PageSettings (LoggedInUserName, PageSize) Values (‘gates’,20)

— Create a Sample Stored Procedure to implement customized paging

CREATE PROCEDURE sp_FetchProducts
(
    @LoginName VARCHAR(128)
)
As
BEGIN

SELECT [ProductID],[Name],[ProductNumber],[MakeFlag],[FinishedGoodsFlag],[Color],[StandardCost],[ListPrice]
  FROM [Production].[Product]
  ORDER BY [Name]
  OFFSET 10 ROWS
  FETCH NEXT (SELECT PageSize From PageSettings WHERE LoggedInUserName=@LoginName) ROWS ONLY 

END

–Execute the Stored Procedure under login “Bill”

EXEC sp_FetchProducts @LoginName = ‘bill’

Output: Stored Procedure returns 10 Records

image

–Execute the Stored Procedure under login “Gates”

EXEC sp_FetchProducts @LoginName = ‘gates’

Output: Stored Procedure now returns 20 Records

image

You can even customize this solution further Table wise as well.

I hope all the SQL developers will enjoy this feature, since it reduces lot of coding for implementing paging using Table Variables or Temp Table or CTEs.