Wednesday, December 30, 2009

Some Sql Server Interview Questions

* Difference between Set and Select
Ans:
1) Set is a ANSI standard for variable assignment.
   Select is a Non-ANSI standard when assigning variables.We can assign only one variable at a time

2) We can assign multiple variable at a time.When assigning from a query that returns more than one value, SET will fail with an error.
   When assigning from a query that returns more than one value, SELECT will assign the last value returned by the query and hide the fact that the query returned

* What is Network Packet Size in SQL
Ans:
NPS(Network Packet Size) is the size of the TDS (tabular data stream) packets used to communicate between your applications and your relational database engine and default packet size is 4 kilobytes and its manily depends on network packet size configuration option.


* How many different locks in SQL SERVER
Ans:
(1)Intent
(2)shared
(3)Update
(4)Exclusive
(5)Schema
(6)Bulk Update

* Diffrence between temp table and table variable
Ans:
(1)Temp Tables are created in the SQL Server TEMPDB database and therefore require more IO resources and locking. Table Variables and Derived Tables are created in memory.

(2)Temp Tables will generally perform better for large amounts of data that can be worked on using parallelism whereas Table Variables are best used for small amounts of data (I use a rule of thumb of 100 or less rows) where parallelism would not provide a significant performance improvement.

(3)You cannot use a stored procedure to insert data into a Table Variable or Derived Table. For example, the following will work: INSERT INTO #MyTempTable EXEC dbo.GetPolicies_sp whereas the following will generate an error: INSERT INTO @MyTableVariable EXEC dbo.GetPolicies_sp.

(4)Derived Tables can only be created from a SELECT statement but can be used within an Insert, Update, or Delete statement.

(5) In order of scope endurance, Temp Tables extend the furthest in scope, followed by Table Variables, and finally Derived Tables.

* What is Cursor
Ans:
  Cursor is a database object used by applications to manipulate data in a set on a row-by-row basis, instead of the typical SQL commands that operate on all the rows in the set at one time. For example, you can use cursor to include a list of all user databases and make multiple operations against each database by passing each database name as a variable

* Write some disadvantage of Cursor
Ans:
  Cursor plays there row quite nicely but although there are some disadvantage of Cursor . Because we know cursor doing roundtrip it will make network line busy and also make time consuming methods. First of all select query gernate output and after that cursor goes one by one so roundtrip happen.Another disadvange of cursor are ther are too costly because they require lot of resources and temporary storage so network is quite busy.

* Can you tell me the difference between DELETE and TRUNCATE commands
Ans:
  Delete command removes the rows from a table based on the condition that we provide with a WHERE clause. Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command.

Thursday, December 24, 2009

How to pad a numeric type column with leading zeros?

Execute the following Microsoft SQL Server T-SQL example scripts to demonstrate SQL padding of numbers and strings with leading and trailing zeros as well as with other designated characters, and techniques
for removing (trim) leading zeros. 



-- SQL Server leading zero - T-SQL padding numbers - lpad tsql - sql pad zero

SELECT ListPrice,

  Padded=RIGHT('0000000000' + CONVERT(VARCHAR,ListPrice), 10)

FROM AdventureWorks2008.Production.Product WHERE ListPrice > 0.0

------------

-- T SQL pad leading zeros - transact sql leading zeros

SELECT ProductID, ReorderPoint = REPLACE(STR(ReorderPoint, 6), SPACE(1), '0')

FROM AdventureWorks2008.Production.Product

/* ProductID            ReorderPoint

      1                 000750

      2                 000750

      3                 000600  */

 ------------

-- SQL Server leading zero - SQL leading zeros - sql server pad leading zero

USE AdventureWorks2008;

DECLARE @Number int = 789

SELECT RIGHT ('000000'+ CAST (@Number AS varchar), 6)

-- 000789

------------

USE AdventureWorks;

-- SQL padding salary pay rate money data type with leading zeroes

-- SQL left pad number - prefix number with zeros - sql server leading zero

-- SQL convert number to text - cast number to varchar string

SELECT EmployeeID,

       Rate,

       PaddedRate = RIGHT(REPLICATE('0',8) + CAST(Rate AS VARCHAR(8)),8)

FROM   HumanResources.EmployeePayHistory
/* Partial results

EmployeeID        Rate              PaddedRate

1                 12.45             00012.45

2                 13.4615           00013.46

3                 43.2692           00043.27

*/


-- SQL zero padding ListPrice money data type - t sql leading zero

-- SQL left pad - T-SQL string concatenation - sql concat

-- SQL convert number to string - pad numeric with zeros

SELECT ProductID,

       ListPrice,

       PaddedListPrice = RIGHT(REPLICATE('0', 8) + CAST(ListPrice AS VARCHAR(8)),8)

FROM Production.Product

/* Results sample

ProductID               ListPrice               PaddedListPrice

965                     742.35                  00742.35

*/


-- SQL month leading zero - sql pad month number with zero

SELECT RIGHT('0' + convert(varchar(2), month(GetDate())), 2)

-- 06
----------

-- trim leading zeros - sql trim leading zeros - remove leading zeros sql

USE AdventureWorks2008;

DECLARE @num  varchar(32)= '00091234560'

SELECT      right(@num, len(@num)+1 - patindex('%[^0]%', @num))

-- 91234560

------------

-- SQL pad numeric data type - SQL pad digits - transact sql leading zeros

-- SQL pad with leading zeroes - append leading zeros - T-SQL top function

-- SQL pad with trailing zeroes - MSSQL append trailing zeros

-- SQL cast money to numeric - cast numeric to string - mssql newid function

SELECT TOP (5)

      ProductName = Name,

      ListPrice = RIGHT(REPLICATE('0', 10)

      + CAST(CAST(ListPrice AS NUMERIC(9,3)) AS VARCHAR) ,10)  

FROM AdventureWorks.Production.Product

ORDER BY NEWID()

/* ProductName                      ListPrice

LL Mountain Frame - Black, 40       000249.790

HL Touring Frame - Yellow, 46       001003.910

Bike Wash - Dissolver               000007.950

Metal Sheet 7                       000000.000

HL Road Frame - Red, 56             001431.500

*/

----------


-- PAD leading zeros function - sql server leading zeros - UDF

USE AdventureWorks2008;

GO

CREATE FUNCTION fnPadNumber

               (@n      DECIMAL(26,2),

                @length TINYINT)

RETURNS VARCHAR(32)

AS

  BEGIN

    RETURN ( replicate('0',@length - len(convert(VARCHAR(32),@n))) +

             convert(VARCHAR(32),@n))

  END

GO


SELECT dbo.fnPadNumber(1234567890.12,16)

-- 0001234567890.12
------------

-- T SQL computed column zero padding - sql generate alphanumeric sequence

USE tempdb; -- SQL Server 2008 T-SQL

CREATE TABLE Celebrity (

  ID           INT    IDENTITY ( 1 , 1 )    PRIMARY KEY,

  CelebrityID  AS 'CEL' + RIGHT('0000' + CAST( ID as varchar),5), -- computed column

  FirstName    VARCHAR(32),

  LastName     VARCHAR(32),

  ModifiedDate DATE    DEFAULT getdate())

GO


INSERT Celebrity

      (FirstName,

       LastName)

VALUES('Jennifer','Aniston'),

      ('Drew','Barrymore'),

      ('Diana','Princess of Wales'),

      ('Tom','Jones'),

      ('Lucille','Ball'),

      ('Frank','Sinatra'),

      ('Elvis','Presley')


SELECT * FROM   Celebrity

GO

-- CelebrityID is zero padded alphanumeric sequence

/* 

ID    CelebrityID       FirstName  LastName          ModifiedDate

1     CEL00001          Jennifer    Aniston          2012-07-04

2     CEL00002          Drew        Barrymore        2012-07-04

3     CEL00003          Diana       Princess of Wales 2012-07-04

4     CEL00004          Tom         Jones             2012-07-04

5     CEL00005          Lucille     Ball              2012-07-04

6     CEL00006          Frank       Sinatra          2012-07-04

7     CEL00007          Elvis       Presley          2012-07-04

*/

-- Cleanup demo

DROP TABLE Celebrity

GO
------------

-- SQL removing leading zeros when no spaces in string - trimming Leading Zeros

USE AdventureWorks2008;

DECLARE @NumberString varchar(16)='000000246'

SELECT REPLACE(LTRIM(REPLACE(@NumberString, '0', ' ')), ' ', '0')

-- 246

------------

-- SQL remove leading zeros - sql trim leading zeros - numeric test

DECLARE @StringWithLeadingZeros    VARCHAR(12) = '000000654321'

SELECT CAST(CAST(@StringWithLeadingZeros AS INT) AS VARCHAR(10))

WHERE ISNUMERIC (@StringWithLeadingZeros)=1

-- 654321

------------

-- LPAD & RPAD string scalar-valued user-defined functions (UDF)

USE AdventureWorks;

GO

-- Left pad string function

CREATE FUNCTION LPAD

               (@SourceString VARCHAR(MAX),

                @FinalLength  INT,

                @PadChar      CHAR(1))

RETURNS VARCHAR(MAX)

AS

  BEGIN

    RETURN

      (SELECT Replicate(@PadChar,@FinalLength - Len(@SourceString)) + @SourceString)

  END

GO


-- T-SQL Test left padding

SELECT LeftPaddedString = dbo.LPAD(Cast(84856 AS VARCHAR),12,'0')

GO

-- 000000084856


-- MSSQL right pad string function

CREATE FUNCTION RPAD

               (@SourceString VARCHAR(MAX),

                @FinalLength  INT,

                @PadChar      CHAR(1))

RETURNS VARCHAR(MAX)

AS

  BEGIN

    RETURN

      (SELECT @SourceString + Replicate(@PadChar,@FinalLength - Len(@SourceString)))

  END

GO


-- Test right padding

SELECT RightPaddedString = dbo.RPAD(Cast(84856 AS VARCHAR),12,'*')

GO

-- 84856*******

----------


-- Padding a money column with leading zeroes - sql convert leading zero

-- SQL convert money data type to string

SELECT PaddedUnitPrice = RIGHT(replicate('0',20) +

                         convert(varchar,UnitPrice,1), 20)

FROM Northwind.dbo.Products

/* Partial results


PaddedUnitPrice

00000000000000018.00

00000000000000019.00

00000000000000010.00

00000000000000022.00

*/


/**************** Zero padding other numeric data ****************/


-- SQL Server 2008 version featuring the LEFT function

-- SQL convert integer to text - convert integer to varchar

USE AdventureWorks2008;

DECLARE @InputNumber int = 522, @OutputLength tinyint = 12

DECLARE @PaddedString char(12)

SET @PaddedString = LEFT( replicate( '0', @OutputLength ),

    @OutputLength - len( @InputNumber ) ) + convert( varchar(12), @InputNumber)

SELECT PaddedNumber=@PaddedString

/* Result


PaddedNumber

000000000522

*/



-- SQL format currency and pad with leading spaces

-- SQL Server lpad to 9 characters

SELECT   TOP (3)  ProductName=Name,

                  Price=   CONVERT(char(9), ListPrice, 1)

FROM Production.Product

WHERE ListPrice > 0.0 ORDER BY Newid()

/*

ProductName                         Price

LL Touring Frame - Blue, 62           333.42

LL Road Seat Assembly                 133.34

Road-250 Red, 58                    2,443.35

*/

------------

-- Padding with zeroes in the middle of string

DECLARE @Number varchar(10)

SET @Number = '99999'

PRINT 'TRK' + REPLICATE('0', 12 - LEN(@Number)) + @Number

SELECT [Zero Padding]='TRK' + REPLICATE('0', 12 - LEN(@Number)) + @Number

-- Result: TRK000000099999


-- Applying the STUFF string function for zero padding

-- SQL convert integer data type to string

DECLARE @SerialNo int, @OutputSize tinyint

SET @OutputSize = 10

SET @SerialNo = 6543

SELECT PaddedSerialNo =  STUFF(replicate('0', @OutputSize),

    @OutputSize - len(@SerialNo)+1, len(@SerialNo), convert(varchar(9),@SerialNo))

-- Result: 0000006543

-- SQL pad integer with 0-s

-- SQL str function - numeric to character conversion

SELECT TOP 5

CAST(replace(str(ProductID,6),' ','0') AS char(6)) AS ProdID

FROM AdventureWorks.Production.Product

ORDER BY Name

/* Results

ProdID

000001

000879

000712

000003

000002

*/


-- SQL pad string with character

-- SQL create function

-- SQL user-defined function

CREATE FUNCTION dbo.fnLeftPadString (

      @Input VARCHAR(255),

      @PadChar CHAR(1),

      @LengthToPad TINYINT

      )

RETURNS VARCHAR(255) AS 

BEGIN

DECLARE @InputLen TINYINT

SET @InputLen = LEN(@Input)

RETURN

   CASE

      WHEN @InputLen < @LengthToPad

      THEN REPLICATE(@PadChar, @LengthToPad - @InputLen) + @Input

      ELSE @Input

   END -- CASE

END -- UDF

GO


-- SQL pad string – left padding - SQL left pad with asterisk

-- SQL check printing - SQL currency formatting

DECLARE @DollarAmount varchar(20)

SET @DollarAmount = '234.40'

SELECT PaddedString='$'+dbo.fnLeftPadString(@DollarAmount, '*', 10)

GO

-- Result: $****234.40


-- SQL currency formatting with asterisk-fill

DECLARE @Amount MONEY

SET @Amount = '3534.40'

SELECT CurrencyFormat = '$' + REPLACE(Convert(char(12),@Amount,1),' ','*')

-- $****3,534.40

SELECT      PaddedProductID =

                  dbo.fnLeftPadString (CONVERT(varchar, ProductID), '0', 6),

            ProductName=Name,

            ListPrice

FROM Production.Product

ORDER BY PaddedProductID

GO


/* Partial results


PaddedProductID         ProductName       ListPrice

000757                  Road-450 Red, 48  1457.99

000758                  Road-450 Red, 52  1457.99

000759                  Road-650 Red, 58  782.99

000760                  Road-650 Red, 60  782.99

000761                  Road-650 Red, 62  782.99

*/

----------

-- Generating tracking numbers

-- SQL pad zeroes

WITH cteSequence(SeqNo)

     AS (SELECT 1

         UNION ALL

         SELECT SeqNo + 1

         FROM   cteSequence

         WHERE  SeqNo < 1000000)

SELECT TOP 100 CAST(('TRK' + REPLICATE('0',

               7 - LEN(CAST(SeqNo AS VARCHAR(6)))) +

               CAST(SeqNo AS VARCHAR(6))) AS VARCHAR(10)) AS TrackingNo

FROM   cteSequence

OPTION (MAXRECURSION 0)

GO

/* Partial results


TrackingNo

TRK0000001

TRK0000002

TRK0000003

TRK0000004

TRK0000005

TRK0000006

TRK0000007

*/

----------

-- SQL server pad

-- SQL str function

-- SQL pad integer

-- SQL left pad

SELECT TOP (4) StaffName=LastName+', '+FirstName,

PaddedEmployeeID = REPLACE(STR(EmployeeID, 6, 0), ' ', '0')

FROM HumanResources.Employee e

INNER JOIN Person.Contact c

      ON e.ContactID = c.ContactID

ORDER BY NEWID()

/* Results


StaffName         PaddedEmployeeID

Dyck, Shelley     000214

Hines, Michael    000039

Ford, Jeffrey     000015

Caron, Rob        000168

*/


-- SQL asterisk padding

-- SQL pad with asterisk

-- SQL right pad

SELECT  TOP ( 2 * 2 )

              AddressID

            , City+REPLICATE('*', 20-len(City)) AS City

            , PostalCode

FROM AdventureWorks.Person.[Address]

WHERE LEN(City) <= 20

ORDER by NEWID()

GO

/*

AddressID   City                          PostalCode

13465       Imperial Beach******    91932

23217       Corvallis***********    97330

18548       Milwaukie***********    97222

24893       Goulburn************    2580

*/

------------

------------

-- SQL left pad any size string Alpha with any length string Beta

------------

-- SQL user-defined function - UDF - scalar-valued string function

-- T-SQL varchar(max)

USE AdventureWorks2008;

GO

CREATE FUNCTION fnMaxPad

               (@SourceString  VARCHAR(MAX),

                @PaddingString VARCHAR(MAX),

                @OutputLength  INT)

RETURNS VARCHAR(MAX)

AS

  BEGIN

    DECLARE  @WorkString VARCHAR(MAX) =

      ISNULL(REPLICATE(@PaddingString,@OutputLength - len(ISNULL(@SourceString,0))),

                            '') + @SourceString

    RETURN RIGHT(@WorkString, @OutputLength)

  END

GO


-- Execute UDF

SELECT TOP ( 5 ) [SQL Padding Demo] =

  dbo.fnMaxPad(CONVERT(VARCHAR,FLOOR(ListPrice)),'_/',21)

FROM     Production.Product

ORDER BY NEWID()

GO

/* Results


SQL Padding Demo

_/_/_/_/_/_/_/2443.00

/_/_/_/_/_/_/_/_/0.00

/_/_/_/_/_/_/_/147.00

/_/_/_/_/_/_/_/_/0.00

_/_/_/_/_/_/_/1003.00

*/

------------

-- SQL left pad unicode string Alpha with any length unicode string Beta

-- MSSQL pad international

-- SQL user-defined function - UDF - scalar-value function

-- T-SQL nvarchar(max)

USE AdventureWorks2008;

GO

CREATE FUNCTION fnMaxPadInternational

               (@SourceString  NVARCHAR(MAX),

                @PaddingString NVARCHAR(MAX),

                @OutputLength  INT)

RETURNS NVARCHAR(MAX)

AS

  BEGIN

    DECLARE  @WorkString NVARCHAR(MAX) =

      ISNULL(REPLICATE(@PaddingString,@OutputLength - len(ISNULL(@SourceString,0))),

                            '') + @SourceString

    

    RETURN RIGHT(@WorkString, @OutputLength)

  END

GO


-- Execute UDF

SELECT TOP ( 5 ) [SQL Padding Demo] =

dbo.fnMaxPadInternational(LEFT(Description,6),'_/',21)

FROM     Production.ProductDescription

ORDER BY NEWID()

GO

/* Results


SQL Padding Demo

/_/_/_/_/_/_/_/ล้อ ที่

/_/_/_/_/_/_/_/Roue d

/_/_/_/_/_/_/_/شوكة ط

/_/_/_/_/_/_/_/Each f

/_/_/_/_/_/_/_/Jeu de

*/

------------
Reference from sqlusa.com

Saturday, December 19, 2009

How to configure SQL Server 2005 to allow remote connections?

To configure SQL Server 2005 to allow remote connections, complete all the following steps.
• Enable remote connections on the instance of SQL Server that you want to connect to from a remote computer.
• Turn on the SQL Server Browser service.
• Configure the firewall to allow network traffic that is related to SQL Server and to the SQL Server Browser service.

Enable remote connections for SQL Server 2005 Express

1. Click Start, point to Programs, point to Microsoft SQL Server 2005, point to Configuration Tools, and then click SQL Server Surface Area Configuration.
2. On the SQL Server 2005 Surface Area Configuration page, click Surface Area Configuration for Services and Connections.
3. On the Surface Area Configuration for Services and Connections page, expand Database Engine, click Remote Connections, click Local and remote connections, click the appropriate protocol to enable for your environment, and then click Apply.
Note Click OK when you receive the following message:
Changes to Connection Settings will not take effect until you restart the Database Engine service.
4. On the Surface Area Configuration for Services and Connections page, expand Database Engine, click Service, click Stop. wait until the MSSQLSERVER service stops, and then click Start to restart the MSSQLSERVER service.

Enable the SQL Server Browser service

1.Click Start, point to Programs, point to Microsoft SQL Server 2005, point to Configuration Tools, and then click SQL Server Surface Area Configuration.
2.On the SQL Server 2005 Surface Area Configuration page, click Surface Area Configuration for Services and Connections.
3.On the Surface Area Configuration for Services and Connections page, click SQL Server Browser, click Automatic for Startup type, and then click Apply.
Note When you click the Automatic option, the SQL Server Browser service starts automatically every time that you start Microsoft Windows.
4.Click Start, and then click OK.

Create exceptions in Windows Firewall

SQL Server 2005 uses an instance ID as part of the path when you install its program files. To create an exception for each instance of SQL Server, you must identify the correct instance ID. To obtain an instance ID, follow these steps:
1. Click Start, point to Programs, point to Microsoft SQL Server 2005, point to Configuration Tools, and then click SQL Server Configuration Manager.
2. In SQL Server Configuration Manager, click the SQL Server Browser service in the right pane, right-click the instance name in the main window, and then click Properties.
3. On the SQL Server Browser Properties page, click the Advanced tab, locate the instance ID in the property list, and then click OK.
To open Windows Firewall, click Start, click Run, type firewall.cpl, and then click OK.
Create an exception for SQL Server 2005 in Windows Firewall
To create an exception for SQL Server 2005 in Windows Firewall, follow these steps:
1. In Windows Firewall, click the Exceptions tab, and then click Add Program.
2. In the Add a Program window, click Browse.
3. Click the C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Binn\sqlservr.exe executable program, click Open, and then click OK.
Note The path may be different depending on where SQL Server 2005 is installed. MSSQL.1 is a placeholder for the instance ID that you obtained in step 3 of the previous procedure.
4. Repeat steps 1 through 3 for each instance of SQL Server 2005 that needs an exception.
Create an exception for the SQL Server Browser service in Windows Firewall
To create an exception for the SQL Server Browser service in Windows Firewall, follow these steps:
1. In Windows Firewall, click the Exceptions tab, and then click Add Program.
2. In the Add a Program window, click Browse.
3. Click the C:\Program Files\Microsoft SQL Server\90\Shared\sqlbrowser.exe executable program, click Open, and then click OK.

---
Hope this helps everyone.

Friday, December 18, 2009

Encryption & Decryption : ASCII encoding

The GetByteCount method determines how many bytes result in encoding a set of Unicode characters, and the GetBytes method performs the actual encoding.

Likewise, the GetCharCount method determines how many characters result in decoding a sequence of bytes, and the GetChars and GetString methods perform the actual decoding.

When selecting the ASCII encoding for your applications, consider the following:

    * The ASCII encoding is usually appropriate for protocols that require ASCII.
    * If your application requires 8-bit encoding, the UTF-8 encoding is recommended over the ASCII encoding. For the characters 0-7F, the results are identical, but use

of UTF-8 avoids data loss by allowing representation of all Unicode characters that are representable. Note that the ASCII encoding has an 8th bit ambiguity that can allow malicious use, but the UTF-8 encoding removes ambiguity about the 8th bit.

    * Previous versions of .NET Framework allowed spoofing by merely ignoring the 8th bit. The current version has been changed so that non-ASCII code points fall back during the decoding of bytes.

——————————————————————
Example of ASCII encoding
——————————————————————

SecurityClass.cs
————————–
public static string EnryptString(string strEncrypted)
{
byte[] b = System.Text.ASCIIEncoding.ASCII.GetBytes(strEncrypted);
string encryptedConnectionString = Convert.ToBase64String(b);
return encryptedConnectionString;
}

public static string DecryptString(string encrString)
{
byte[] b = Convert.FromBase64String(encrString);
string decryptedConnectionString = System.Text.ASCIIEncoding.ASCII.GetString(b);
return decryptedConnectionString;
}

Default.aspx.cs
———————
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
string Password = “SandeepMRamani”;
lblOriginal.Text = Password;
lblEncryption.Text = SecurityClass.EnryptString(Password);
lblDecryption.Text = SecurityClass.DecryptString(lblEncryption.Text);
}
}
Default.aspx
——————
<div align=”center” style=”font-size:xx-large;”>
<h1> Encryption / Decryption Example </h1>
<hr />

Original String :
<asp:Label ID=”lblOriginal” style=”font-weight:bolder;” runat=”server” Text=”"></asp:Label>
<br />
Encrypted Text :
<asp:Label ID=”lblEncryption” style=”font-weight:bolder;” runat=”server” Text=”"></asp:Label>
<br />
Decrypted Text :
<asp:Label ID=”lblDecryption” style=”font-weight:bolder;” runat=”server” Text=”"></asp:Label>
<hr />
</div>

--

Happy programming

Differences between varchar and nvarchar in SQL Server

=>SQL Server 2000 and SQL Server 7, a row cannot exceed 8000 bytes in size. This means that a VARBINARY column can only store 8000 bytes (assuming it is the only column in a table), a VARCHAR column can store up to 8000 characters and an NVARCHAR column can store up to 4000 characters (2 bytes per unicode character). This limitation stems from the 8 KB internal page size SQL Server uses to save data to disk.
To store more data in a single column, you needed to use the TEXT, NTEXT, or IMAGE data types (BLOBs) which are stored in a collection of 8 KB data pages that are separate from the data pages that store the other data in the same table. These data pages are arranged in a B-tree structure. BLOBs are hard to work with and manipulate. They cannot be used as variables in a procedure or a function and they cannot be used inside string functions such as REPLACE, CHARINDEX or SUBSTRING. In most cases, you have to use READTEXT, WRITETEXT, and UPDATETEXT commands to manipulate BLOBs.

To solve this problem, Microsoft introduced the VARCHAR(MAX),  NVARCHAR(MAX), and VARBINARY(MAX) data types in SQL Server 2005. These data types can hold the same amount of data BLOBs can hold (2 GB) and they are stored in the same type of data pages used for other data types. When data in a MAX data type exceeds 8 KB, an over-flow page is used. SQL Server 2005 automatically assigns an over-flow indicator to the page and knows how to manipulate data rows the same way it manipulates other data types. You can declare variables of MAX data types inside a stored procedure or function and even pass them as variables. You can also use them inside string functions.



The broad range of data types in SQL Server can sometimes throw people through a loop, especially when the data types seem to be highly interchangeable. Two in particular that constantly spark questions are VARCHAR and NVARCHAR: what's the difference between the two, and how important is the difference? VARCHAR is an abbreviation for variable-length character string. It's a string of text characters that can be as large as the page size for the database table holding the column in question. The size for a table page is 8,196 bytes, and no one row in a table can be more than 8,060 characters. This in turn limits the maximum size of a VARCHAR to 8,000 bytes.
The "N" in NVARCHAR means uNicode. Essentially, NVARCHAR is nothing more than a VARCHAR that supports two-byte characters. The most common use for this sort of thing is to store character data that is a mixture of English and non-English symbols — in my case, English and Japanese.
The key difference between the two data types is how they're stored. VARCHAR is stored as regular 8-bit data. But NVARCHAR strings are stored in the database as UTF-16 — 16 bits or two bytes per character, all the time — and converted to whatever codepage is being used by the database connection on output (typically UTF-8). That said, NVARCHAR strings have the same length restrictions as their VARCHAR cousins — 8,000 bytes. However, since NVARCHARs use two bytes for each character, that means a given NVARCHAR can only hold 4,000 characters (not bytes) maximum. So, the amount of storage needed for NVARCHAR entities is going to be twice whatever you'd allocate for a plain old VARCHAR.
Because of this, some people may not want to use NVARCHAR universally, and may want to fall back on VARCHAR — which takes up less space per row — whenever possible.


Thursday, December 17, 2009

How to dynamically adjust an iframe’s height?

I was looking to display content of the other aspx page inside iframe but i wasnt able to adjust the height of the iframe. so try out this solution to resolve it.

Insert iframe on page
   <iframe scrolling='no' frameborder='0' id='frmid' src=’getad.aspx'
            onload='javascript:resizeIframe(this);'>
   </iframe>


Use this javascript to resize iframe based on the height & width of child page




<script language="javascript" type="text/javascript">
 function resizeIframe(obj)
 {
   obj.style.height = obj.contentWindow.document.body.scrollHeight + 'px';
   obj.style.width = obj.contentWindow.document.body.scrollWidth + 'px';
 }
 </script>


What does this code do? When the body of the parent frame loads, it looks up the document element “childframe” which corresponds to the iframe. Then the page calls a function resizeFrame(). The function sets the height of the frame to be the scrollHeight, which effectively removes the scrollbar.

happy programming!

Wednesday, December 2, 2009

Parameter Sniffing and OPTIMZE FOR

Parameter Sniffing refers to a process whereby SQL Server’s execution environment “sniffs” the parameter values during first invocation, and passes it along to the query optimizer so that they can be used to generate optimal query execution plans.


While parameter sniffing is certainly a powerful feature, it can cause problems when a procedure’s plan happens to have been kicked out of the procedure cache (or was never in it) just prior to the procedure being called with atypical parameter values. This can result in a plan that is skewed toward atypical use, one that is not optimal when called with typical values. Since, once cached, a query plan can be reused for parameter values that vary widely, the ideal situation is to have a plan in the cache that covers the typical usage of the procedure as much as possible. If a plan makes it into the cache that is oriented toward atypical parameter values, it can have a devastating effect on performance when executed with typical values. 

Click here to read full article.

Ideal SQL Query For Handling Error & Transcation in MS SQL

BEGIN TRY BEGIN TRAN --put queries here COMMIT; END TRY BEGIN CATCH IF @@TRANCOUNT>0 BEGIN SELECT @@ERROR,ERRO...