Magic table in SQL ?

Magic tables are nothing but INSERTED, DELETED table scope level, These are not physical tables, only Internal tables.

This Magic table are used In SQL Server 6.5, 7.0 & 2000 versions with Triggers only. But, In SQL Server 2005, 2008 & 2008 R2 Versions can use these Magic tables with Triggers and Non-Triggers also.

Using with Triggers:If you have implemented any trigger for any Tables then,
1.Whenever you Insert a record on that table, That record will be there on INSERTED Magic table.
2.Whenever you Update the record on that table, That existing record will be there on DELETED Magic table and modified New data with be there in INSERTED Magic table.
3.Whenever you Delete the record on that table, That record will be there on DELETED Magic table Only.

These magic table are used inside the Triggers for tracking the data transaction.
Using Non-Triggers:You can also use the Magic tables with Non-Trigger activities using OUTPUT Clause in SQL Server 2005, 2008 & 2008 R2 versions.

Line Break In SQL Sever...

I need to format a string, like separate lines.  While displaying that string i need split into two lines. To do that follow the bellow steps. we have two different options to get new line.

What is difference between Line Feed (\n) and Carriage Return (\r)?

   1. Line Feed – LF – \n – 0x0a – 10 (decimal)
   2. Carriage Return – CR – \r – 0x0D – 13 (decimal)
Different operating systems have a different way of understanding new line. Mac only understands ‘\r’ as new line, while Unix and Linux understand ‘\n’ as new line character. Our favorite OS windows needs both the characters together to interpret as new line, which is ‘\r\n’. This is the reason why a file created in one OS does not open properly in another OS and makes it messy.

we can create a new line in SQL Server. It is a very simple script yet very useful when we have to do run print something or generate scripts. Here is two examples below that are very easy to understand. In the first example, there are no new line chars inserted and for the same, everything is displayed in a single line. However, in the second example, new line char is inserted and the lines are separated with a new line.

Example 1: No new line feed char

DECLARE @NewLineChar AS CHAR(2) = CHAR(13) + CHAR(10)
PRINT ('SELECT FirstLine AS FL SELECT SecondLine AS SL' )
GO

Example 2: With new line feed char

DECLARE @NewLineChar AS CHAR(2) = CHAR(13) + CHAR(10)
PRINT ('SELECT FirstLine AS FL ' +@NewLineChar +'SELECT SecondLine AS SL' )
GO

Claim DB Space After Deleting Records in Table - Reduce DB Space

Recently I have deleted unwanted records from my SQL server database table, what i realise is even after deleting records, space used by database is not reducing.  After browsing help available on Internet, I found out

1) Whenever we delete records from table, sql server doesn't reduce size of database immediately.
2) Even after deleting table , sql server doesn't reduce size of database.
3) Instead of Freeing space for deleted records, sql server marks pages containing deleted records as free pages, showing that they belong to the table. When new data are inserted, they are put into those pages first. Once those pages are filled up, SQL Server will allocate new pages.

So In order to claim database space after deleting records in Table, go through following steps:
1) Check what is Size of your Database using following command?EXEC SP_SPACEUSED

2) Delete Records from table, If you have already did that skip this step.

3) Run below command to claim unused database space.
DBCC SHRINKDATABASE(0)

DBCC SHRINKDATABASE command - Shrinks the size of the data and log files in the specified database.

Best Practise to use this command1. 
1.A shrink operation is most effective after an operation that creates lots of unused space, such as a truncate table or a drop table operation.

2. Most databases require some free space to be available for regular day-to-day operations. If you shrink a database repeatedly and notice that the database size grows again, this indicates that the space that was shrunk is required for regular operations. In these cases, repeatedly shrinking the database is a wasted operation.
3. A shrink operation does not preserve the fragmentation state of indexes in the database, and generally increases fragmentation to a degree. This is another reason not to repeatedly shrink the database.

More reading on this command
http://msdn.microsoft.com/en-us/library/ms190488.aspx 

http://dotnetguts.blogspot.in/2011/02/claim-db-space-after-deleting-records.html

http://blog.sqlauthority.com/2010/09/07/sql-server-index-levels-and-delete-operations-page-level-observation/

What is a Common Table Expression (CTE)

For any operation over a temporary result set, what are the options SEL Server has to offer? We do have a Temp table, a table variable, table valued parameters and of course not to forget table valued function. But with the onset of SQL Server 2005 and onwards, a very powerful feather has been added for the programmers' benefit: Common Table Expression (CTE). It simplifies complex queries and most importantly enables you to recurs.


A CTE can be thought of as a temporary result set and are similar to a derived table in that it is not stored as an object and lasts only for the duration of the query. A CTE is generally considered to be more readable than a derived table and does not require the extra effort of declaring a Temp Table while providing the same benefits to the user. However; a CTE is more powerful than a derived table as it can also be self-referencing, or even referenced multiple times in the same query.



Background:
Most of the developers while writing the stored procedures they create the temp tables or table variables. They need some table to store the temporary results in order to manipulate the data in the other tables based on this temp result.
The temp variables will be stored on the tempdb and it needs to be deleted in the tempdb database.
The table variable is best when compare with the temp tables. Because the table variable initially will be there in the memory for the certain limit of size and if the size increase then it will be moved to the temp database. However the scope of the table variable is only up to that program. When compare with table variable the CTE is best. It just store the result set like normal view.
CTE (Common Table Expression):
The CTE is one of the essential features in the sql server 2005.It just store the result as temp result set. It can be access like normal table or view. This is only up to that scope. 


The syntax of the CTE is the following.
WITH name (Alias name of the retrieve result set fields)
AS
(
//Write the sql query here
)
SELECT * FROM name
Here the select statement must be very next to the CTE. The name is mandatory and the argument is an optional. This can be used to give the alias to the retrieve field of the CTE.
CTE 1: Simple CTE
WITH ProductCTE
AS(  SELECT ProductID AS [ID],ProductName  AS [Name],CategoryID  AS  [CID],UnitPrice  AS  [Price]
  FROM Products
)SELECT * FROM ProductCTE
Here all the product details like ID, name, category ID and Unit Price will be retrieved and stored as temporary result set in the ProductCTE.


This result set can be retrieved like table or view.


CTE2:Simple CTE with alias 
WITH ProductCTE(ID,Name,Category,Price)AS(  SELECT ProductID,ProductName,CategoryID,UnitPrice
  FROM Products
)SELECT * FROM ProductCTE
Here there are four fieds retrieves from the Products and the alias name have given in the arqument to the CTE result set name.


It also accepts like the following as it is in the normal select query.
WITH ProductCTE
AS(  SELECT ProductID AS [ID],ProductName AS [Name],CategoryID AS [CID],UnitPrice AS [Price]
  FROM Products
)SELECT * FROM ProductCTE


CTE 3: CTE joins with normal table
The result set of the CTE can be joined with any table and also can enforce the relationship with the CTE and other tables.
WITH OrderCustomer
AS(  SELECT DISTINCT CustomerID FROM Orders
)SELECT C.CustomerID,C.CompanyName,C.ContactName,C.Address+', '+C.City AS [Address] FROMCustomers C INNER JOIN OrderCustomer OC ON OC.CustomerID = C.CustomerID
Here the Ordered Customers will be placed in the CTE result set and it will be joined with the Customers details.
CTE 4: Multiple resultsets in the CTE
WITH MyCTE1
AS(  SELECT ProductID,SupplierID,CategoryID,UnitPrice,ProductName FROM Products
), 
MyCTE2
AS(  SELECT DISTINCT ProductID FROM "Order Details"
)SELECT C1.ProductID,C1.ProductName,C1.SupplierID,C1.CategoryID FROM MyCTE1 C1 INNER JOINMyCTE2 C2 ON C1.ProductID = C2.ProductID
Here, there are two result sets that will be filtered based on the join condition.


CTE 5: Union statements in the CTE
WITH PartProdCateSale
AS(SELECT ProductID FROM Products WHERE CategoryID = (SELECT CategoryID FROM CategoriesWHERE CategoryName='Condiments')UNION ALL
SELECT ProductID FROM Products WHERE CategoryID = (SELECT CategoryID FROM CategoriesWHERE CategoryName='Seafood')
)SELECT OD.ProductID,SUM(OD.UnitPrice*OD.Quantity) AS [Total Sale] FROM "Order Details" ODINNER JOIN PartProdCateSale PPCS ON PPCS.ProductID = OD.ProductID
GROUP BY OD.ProductID
Normally when we combine the many result sets we create table and then insert into that table. But see here, we have combined with the union all and instead of table, here CTE has used.


CTE 6: CTE with identity column
WITH MyCustomCTE
   AS   (      SELECT CustomerID,row_number() OVER (ORDER BY CustomerID) AS iNo FROM 
         Customers
   )SELECT * FROM MyCustomCTE
Conclusion:
I hope that the CTE will be very useful in the sql server. When we work the web applications the performance must be consider in the both front-end and Back-end. First we must retrieve the result effectively in the back end.



Reference Links:
http://www.codeproject.com/Articles/275645/CTE-In-SQL-Server
http://msdn.microsoft.com/en-us/library/ms190766.aspx
http://www.simple-talk.com/sql/t-sql-programming/sql-server-cte-basics/
http://www.sqllion.com/2010/08/common-table-expressions-cte/
http://www.sqlservercentral.com/articles/Development/commontableexpressionsinsqlserver2005/1758/

SSIS to SQL Server Data Type Translations

While implementing SSIS package i have faced conversion problems SSIS data types. So here is bellow chart SSIS data types to SQL Server data types. 

SSIS Data Type	SSIS Expression	SQL Server
single-byte signed integer	(DT_I1)
two-byte signed integer	(DT_I2)	smallint
four-byte signed integer	(DT_I4)	int
eight-byte signed integer	(DT_I8)	bigint
single-byte unsigned integer	(DT_UI1)	tinyint
two-byte unsigned integer	(DT_UI2)
four-byte unsigned integer	(DT_UI4)
eight-byte unsigned integer	(DT_UI8)
float	(DT_R4)	real
double-precision float	(DT_R8)	float
string	(DT_STR, «length», «code_page»)	char, varchar
Unicode text stream	(DT_WSTR, «length»)	nchar, nvarchar, sql_variant, xml
date	(DT_DATE)	date
Boolean	(DT_BOOL)	bit
numeric	(DT_NUMERIC, «precision», «scale»)	decimal, numeric
decimal	(DT_DECIMAL, «scale»)	decimal
currency	(DT_CY)	smallmoney, money
unique identifier	(DT_GUID)	uniqueidentifier
byte stream	(DT_BYTES, «length»)	binary, varbinary, timestamp
database date	(DT_DBDATE)	date
database time	(DT_DBTIME)
database time with precision	(DT_DBTIME2, «scale»)	time(p)
database timestamp	(DT_DBTIMESTAMP)	datetime, smalldatetime
database timestamp with precision	(DT_DBTIMESTAMP2, «scale»)	datetime2
database timestamp with timezone	(DT_DBTIMESTAMPOFFSET, «scale»)	datetimeoffset(p)
file timestamp	(DT_FILETIME)
image	(DT_IMAGE)	image
text stream	(DT_TEXT, «code_page»)	text
Unicode string	(DT_NTEXT)	ntext

Reference Links
http://www.bidn.com/blogs/DevinKnight/ssis/1387/ssis-to-sql-server-data-type-translations
http://www.sqlservercentral.com/blogs/dknight/2010/12/22/ssis-to-sql-server-data-type-translations/