Saturday, 27 June 2009

How to generate Sequence number in SQL Server

Sequence number generation is one of the common requirements in all the OLTP applications.SQL Server supports many ways to generate Sequence numbers. The below example explains how to generate multiple sequences dynamically using the SQL Server

Schema Design

This table will hold the configuration parameters for each of the Sequence Types (eg: PurchaseOrder, GRN etc).The column “SequenceName” column will have the unique code for each Sequence type and the “TableName” column is used to map the name of the “IDGenerator” table. (I.e. multiple IDGenerator tables can be created with the same structure and mapped accordingly)

ID Generation:
The below stored procedure pGetSEQID is used to generate the new sequence number .It accepts the table name as input and return the new sequence number. Since the IDGenerator table can be different for each ID type the stored procedure is written as dynamic.


CREATE PROCEDURE pGetSEQID (
@P_SEQTableName VARCHAR(30)
)
AS
BEGIN
DECLARE @V_SEQValue BIGINT
DECLARE @V_SQLString NVARCHAR(200)
DECLARE @V_ParmDefinition NVARCHAR(200)
DECLARE @V_SEQTableName VARCHAR(30)
SET @V_ParmDefinition = N'@V_SEQValue BIGINT OUTPUT'
SET @V_SQLString = N'INSERT INTO ' +
@P_SEQTableName +
N'(Status) values (''Y'') SELECT @V_SEQValue = SCOPE_IDENTITY()'
exec sp_executesql @V_SQLString,@V_ParmDefinition ,@V_SEQValue =@V_SEQValue OUTPUT
SELECT @V_SEQValue NewSequenceValue
END


EXEC pGetSEQID ‘PurchaseOrder’ will generate the Sequence Number for ID type purchase order

We can make use of Prefix and Suffix columns in the IDParamter table to generate the Sequence number with the required format
Eg: “BL0001” , BL100/0908

Tuesday, 16 June 2009

How to Select Data in Random Order in SQL Server

In number of scenarios we might want to do data sampling or select the data in a Random Order. SQL Server supports various options for data sampling. I have given some of the examples here

Using NEWID() :
SELECT TOP 10 ForeName
FROM Patient
ORDER BY NEWID()


Using PERCENT
SELECT TOP 10 ForeName
FROM (SELECT TOP 30 PERCENT ForeName
FROM Patient
ORDER BY ForeName ASC) AS Pat
ORDER BY 1 DESC

Friday, 8 May 2009

How to find the Database Restore Details in SQL Server 2008

It is often useful to know the details from where the database is restored.The restore history of the database is stored in the msdb table "restorehistory".I recently came across this query which gives the complete information of restore history including the Restored Login , From & To Location of the Files

SELECT
rsh.destination_database_name AS [Database],
rsh.user_name AS [Restored By],
CASE WHEN rsh.restore_type = 'D' THEN 'Database'
WHEN rsh.restore_type = 'F' THEN 'File'
WHEN rsh.restore_type = 'G' THEN 'Filegroup'
WHEN rsh.restore_type = 'I' THEN 'Differential'
WHEN rsh.restore_type = 'L' THEN 'Log'
WHEN rsh.restore_type = 'V' THEN 'Verifyonly'
WHEN rsh.restore_type = 'R' THEN 'Revert'
ELSE rsh.restore_type
END AS [Restore Type],
rsh.restore_date AS [Restore Started],
bmf.physical_device_name AS [Restored From],
rf.destination_phys_name AS [Restored To]
FROM msdb.dbo.restorehistory rsh
INNER JOIN msdb.dbo.backupset bs ON rsh.backup_set_id = bs.backup_set_id
INNER JOIN msdb.dbo.restorefile rf ON rsh.restore_history_id = rf.restore_history_id
INNER JOIN msdb.dbo.backupmediafamily bmf ON bmf.media_set_id = bs.media_set_id


You can apply filter criteria such as the restore date , Database by addding a where clause to the existing query as shown below

WHERE
rsh.restore_date >= DATEADD(dd, "No of Past Days" , GETDATE())
AND destination_database_name = ISNULL( "DB Name", destination_database_name)
ORDER BY rsh.restore_history_id DESC


Tuesday, 5 May 2009

SQL Server 2008 - Performance white paper

Microsoft has release its latest white paper on SQL Server 2008 performance trouble shooting.This article provides steps to diagonse the common performance problems faced by Microsoft CSS team.The following areas are covered in depth
  • CPU Bottlenecks
  • Memory Bottlenecks
  • IO Bottlenecks
  • Temp DB
  • Slow Running Queries
  • Extended Events
  • Data Collector & MDV
The new features of SQL Server 2008 such as Extended Events & Data Collector are covered in detail .It is worth to have a look at this long running ( 102 pages) document. It is avilable for download at
http://msdn.microsoft.com/en-us/library/dd672789.aspx

Monday, 13 April 2009

SQL Server 2008 SP1- Released

Microsoft has released the latest service pack for SQL Server 2008 with the following key improvements
  • SlipStream - The SQL Server 2008 and Service Pack 1 installation can be integrated and installed in a single step.
  • Service Pack Uninstall – We can uninstall the service pack alone ( no need to un install the entire service)
  • Report Builder 2.0 Click Once capability

It is available for download at

http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=66ab3dbb-bf3e-4f46-9559-ccc6a4f9dc19

Wednesday, 11 February 2009

SQL Server 2008 DMV's Relationship mapping

Microsoft has introduced the concept of DMV’s (Dynamic Management Views) in SQL Server 2005 and concept is extended to SQL Server 2008 also with additional DMV's for mirroring , memory management etc.

Microsoft has recently released the latest “System Views Map” for SQL Server 2008 which shows the key system views and the relationships between them. You can download the latest System Views Map at

http://www.microsoft.com/downloads/details.aspx?FamilyID=531c53e7-8a2a-4375-8f2f-5d799aa67b5c&displaylang=en

The updated “System views Map” for SQ Server 2005 also can be downloaded at

http://www.microsoft.com/downloads/details.aspx?familyid=2EC9E842-40BE-4321-9B56-92FD3860FB32&displaylang=en

SQL Server Hot Fixes at one place

Microsoft is now days releasing lot of hot fixes for its products’ recently found one TechNet blog which is specific to hot fixes. This is one place where you can find the cumulative update of each hot fixes / updates released for SQL Server, also it has the release note information linked to the knowledge base articles.

This blog also contains hot fix information for other Microsoft products such as Windows, Visual Studio, and IE etc. The original blog can be find at

http://blogs.technet.com/hot/archive/tags/SQL+Server/default.aspx