MERGE Command in SQL Server

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MERGE Command in SQL Server

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In SQL Server 2008, Microsoft introduces the MERGE functionality through the MERGE command. The MERGE command inserts rows that don’t exist and updates the rows that do exist.

    What MERGE Command works as,

        IF FOUND

           THEN UPDATE

        ELSE

           INSERT;

    Until now, this MERGE functionality could only be made available in SQL Server through stored procedures and cursors, etc.

    This article illustrates how to user MERGE command in SQL Server 2008.

    Suppose we have 2 tables with same field structure as ID, ProductName and SKU,

        MERGE INTO ProductTable1 AS Target

        USING  AS ProductTable2 AS Source

                ON Target.ID = Source.ID

        WHEN MATCHED THEN

                UPDATE SET Target.ProductName = Source.ProductName,

                Target.SKU = Source.SKU

        WHEN NOT MATCHED THEN

                INSERT (ID,ProductName,SKU) VALUES (Source.ID,Source.ProductName,Source.SKU);

 


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CASE (Transact SQL)

Evaluates a list of conditions and returns one of multiple possible result expressions.

CASE has two formats:

· The simple CASE function compares an expression to a set of simple expressions to determine the result.

· The searched CASE function evaluates a set of Boolean expressions to determine the result.

Examples:

A. Using a SELECT statement with a simple CASE function

Within a SELECT statement, a simple CASE function allows for only an equality check; no other comparisons are made. The following example uses the CASE function to change the display of product line categories to make them more understandable.

USE AdventureWorks;
GO
SELECT   ProductNumber, Category =
CASE ProductLine
WHEN ‘R’ THEN ‘Road’
WHEN ‘M’ THEN ‘Mountain’
WHEN ‘T’ THEN ‘Touring’
WHEN ‘S’ THEN ‘Other sale items’
ELSE ‘Not for sale’
END,
Name
FROM Production.Product
ORDER BY ProductNumber;
GO

B. Using a SELECT statement with a searched CASE function

Within a SELECT statement, the searched CASE function allows for values to be replaced in the result set based on comparison values. The following example displays the list price as a text comment based on the price range for a product.

USE AdventureWorks;
GO
SELECT   ProductNumber, Name, ‘Price Range’ =
CASE
WHEN ListPrice =  0 THEN ‘Mfg item – not for resale’
WHEN ListPrice < 50 THEN ‘Under $50’
WHEN ListPrice >= 50 and ListPrice < 250 THEN ‘Under $250’
WHEN ListPrice >= 250 and ListPrice < 1000 THEN ‘Under $1000’
ELSE ‘Over $1000’
END
FROM Production.Product
ORDER BY ProductNumber ;
GO


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Paging in SQL Server

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Web Application Performance (Paging in Sql Server)

As a Web developer, you know by now that using the default paging capabilities of ASP.NET Webcontrols like DataGrid and GridView cause the Performance issue when we have thousands and thousands of records in our database; because with every roundtrip to the data-server, you get ALL the records ALL of the time. This is fine perhaps for very small databases. But in web application, you always have to count on its Performance.

One alternate approach to this scenario is to serve “On Demand” records. That is; for example; retrieving 1-100 records, then 101-200 records result set based on some event rather than retrieving all the records all of the time. I am talking about “Paging in Sql Server”.

My-SQL

The simplest solution is provided by My-SQL using LIMIT keyword. Check out the below Query:

Select * From Product Limits 15,5

It will retrieve results from 16 to 20 records. In above Query, 15 if the offset from where you want the result set records and 5 is the number of records you want to retrieve.

Sql Server 2005

Unfortunately, SQL Server does not have an equivalent to “Limit” keyword. Its nearest is TOP N, which returns the first N rows. Still there are two alternative than we can use for “Paging”.

Using ROW_NUMBER()

Sql 2005 includes the ROW_NUMBER() function, which adds an integer field to each record. In other words, it adds the record’s position within the result set as an additional field so that the first record has a 1, the second a 2, etc.

To ensure the numbering is consistent, however, SQL Server needs to know how to sort the data. Because of this, ROW_NUMBER() must immediately be followed by the OVER() function. OVER() has one required parameter, which is an ORDER BY clause. The basic syntax is:

SELECT ROW_NUMBER() OVER(ORDER BY [Name]) as RowNum,

[Name], [SKU], [ManufacturerPartNumber]

FROM Product

The Product data in result set will be appeared sorted by Name, and it has an extra column indicating each record’s position within the results.

If we want to limit the results displayed to a certain range, we need to nest this SELECT inside another one. To limit our results to records 5 to 10, we can use the following query:

SELECT * FROM

(SELECT ROW_NUMBER() OVER(ORDER BY [Name]) AS RowNum,

[Name], [SKU], [ManufacturerPartNumber] FROM Product) AS Product1

WHERE RowNum >= 5 AND RowNum <= 10

With Nested Queries

There is one another solution that consists only of 1 sql-statement, and so is efficient and quick, even with large databases. The good news is : it will work ! Always ! it’s looking rather a bit complicated; but its not!

Let us see the Example directly to limit our results to records 6 through 10,

SELECT P.[Name], P.[SKU], P.[ManufacturerPartNumber] FROM (

SELECT TOP 5 [ProductID],[Name] FROM (

SELECT TOP 10 [ProductID],[Name]

FROM Product

ORDER BY Product.[Name] ASC) as Product1

ORDER by Product1.[Name] DESC) as Product2

INNER JOIN Product P ON Product2.ProductID = P.ProductID

ORDER by Product2.[Name] ASC

Where 5 is the number of rows you want to retrieve and 10 is the offset.

The innermost Sql Statement will fetch 10 records (1 to 10) Order by Product Name in Ascending Order.

This means that if you have a table with 10,000 records, and you want to have the last 10 records, the innermost SELECT statement will indeed retrieve 10,000 records. This of course has it’s ramifications on performance, but since it’s only the primary key fields (which are indexed) and optionally some sort fields, the impact will be minimal.

The middle Sql Statement will fetch 5 records (10 to 6) Order by Product Name in Descending Order. And Finally the Outer Sql Stateement is simply select statement that will fetch the result in Ascending Order (6 to 10). In Innermost and Midddle Sql Statement only primary key fields or the fields which are indexed are used.

After looking at this in Query Analyzer, it appears that the extra nesting does not add very much to the load. The SQL statement plays with the sorting orders to limit the records, thus resulting in paged recordsets. This means that there should be at least ONE field to be sorted. If there isn’t any, sort on the primary key field(s) !


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Using TRY-CATCH to Rollback a Transaction in the Face of an Error

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Error Handing in Sql Server 2005.
The release of Sql Server 2005 has provided us somany features over its predecessor. No doubt that more preference is given to the tasks performed by the administrator. But there are some new development features added to make your Sql Code more powerful and error resistance, specially; Stored Procedures.
The Feature – “TRY…CATCH”
The Most impressive functionality improvement added for developers is “Exceptional Handling” technique. There is no beneficial reason if you are not writing your code in “Try.. Catch” block.
• A TRY Block – the TRY block contains the code / script that might cause an exception
• A CATCH Block – if an exception occurs from one of the statements in the TRY block, control is branched to the CATCH block, where the exception can be handled, logged, and so on.
Checking @@ERROR – the “sql 2000” Way of Handling Errors in Stored Procedure
Just have a look at below Store Procedure example.
CREATE PROC usp_AccountTransaction
@AccountNum INT,
@Amount DECIMAL
AS
BEGIN
BEGIN TRANSACTION –beginning a transaction..
UPDATE MyChecking SET Amount = Amount – @Amount
WHERE AccountNum = @AccountNum
IF @@ERROR != 0 –check @@ERROR variable after each DML statements..
BEGIN
ROLLBACK TRANSACTION –RollBack Transaction if Error..
RETURN
END
ELSE
BEGIN
UPDATE MySavings SET Amount = Amount + @Amount
WHERE AccountNum = @AccountNum
IF @@ERROR != 0 –check @@ERROR variable after each DML statements..
BEGIN
ROLLBACK TRANSACTION –RollBack Transaction if Error..
RETURN
END
ELSE
BEGIN
COMMIT TRANSACTION –finally, Commit the transaction if Success..
RETURN
END
END
END
GO
Yes!.. This is what we used to code a Stored Procedure in Sql 2000; Check for @@ERROR after every DML (Data Manipulation) Statements and Commit / RollBack the transaction.
While working with SQL Server 2000, detecting errors could only be handled by checking a global error variable, @@ERROR. Because the @@ERROR variable value is reset after each SQL statement, this leads to rather bloated stored procedures, as the variable must be checked after each statement with code to handle any problems.
The TRY…CATCH block in SQL Server 2005 offers a much more readable syntax and one that developers are more familiar with. And yes, SQL Server 2005 still supports to @@ERROR Approach. In this article we’ll look at the new TRY…CATCH block and examine how it can be used to rollback a transaction in the face of an error. Lets move on to it!
Handling Errors With SQL Server 2005’s TRY…CATCH Blocks
In Fact, there is really nothing new to be describe and discuss on TRY…CATCH Block; as we all know with any programming languages, TRY…CATCH block executes a number of statements in the TRY block. If there are no errors in any of the statements, control proceeds to after the CATCH block. If, however, one of the statements causes an error, control branches immediately to the start of the CATCH block.
Basic Syntax is,
BEGIN TRY
Try Statement 1
Try Statement 2

Try Statement M
END TRY
BEGIN CATCH
Catch Statement 1
Catch Statement 2

Catch Statement N
END CATCH

The following system functions are available in the CATCH block and can be used to determine additional error information:
Function                           Description
ERROR_NUMBER()             Returns the number of the error.
ERROR_SEVERITY()           Returns the severity.
ERROR_STATE()                 Returns the error state number.
ERROR_PROCEDURE()       Returns the name of the stored procedure  where the error occurred.
ERROR_LINE()                   Returns the line number inside the routine that caused the error.
ERROR_MESSAGE()            Returns the complete text of the error message.

Take a look at below example,
BEGIN TRY
SELECT GETDATE()
SELECT 1/0–Evergreen divide by zero example!
END TRY
BEGIN CATCH
SELECT ‘There was an error! ‘ + ERROR_MESSAGE()
RETURN
END CATCH;
Using TRY…CATCH to Rollback a Transaction in the Face of an Error
As you saw in earlier example, one of the downsides of the @@ERROR variable approach is that to implement Transaction; we must check this variable after each and every DML SQL statement to determine if an error occurred and, if so, to rollback the transaction. With SQL Server 2005’s TRY…CATCH block, however, these types of scripts are greatly simplified.
Lets Alter the Previous Example!
ALTER PROC usp_AccountTransaction
@AccountNum INT,
@Amount DECIMAL
AS
BEGIN
BEGIN TRY –Start the Try Block..
BEGIN TRANSACTION — Start the transaction..
UPDATE MyChecking SET Amount = Amount – @Amount
WHERE AccountNum = @AccountNum
UPDATE MySavings SET Amount = Amount + @Amount
WHERE AccountNum = @AccountNum
COMMIT TRAN — Transaction Success!
END TRY
BEGIN CATCH
IF @@TRANCOUNT > 0
ROLLBACK TRAN –RollBack in case of Error
— you can Raise ERROR with RAISEERROR() Statement including the details of the exception
RAISERROR(ERROR_MESSAGE(), ERROR_SEVERITY(), 1)
END CATCH
END
GO
Just look at the simplicity and line of code than previous example!
In the TRY block a transaction is started and the two UPDATE statements are performed. If both UPDATEs succeed, the COMMIT will be reached and the transaction committed. If, however, either one produces an error, control will be execute CATCH block where the transaction will be rolled back.
Also, you can “re-raises” the error (using RAISERROR) so that the error information will be passed up to your .Net application from where you are calling the Stored Procedure, in case if you want to use the error information to process further steps anyhow.


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New in C-Sharp 3.0

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New in C-Sharp 3.0

New in C# 3.0
This article discusses the following major new enhancements expected in C# 3.0:
• Implicitly typed local variables
• Anonymous types
• Extension methods
• Object and collection initializers
• Lambda expressions
• Query expressions
• Expression Trees

Implicitly typed local variables:
C# 3.0 introduces a new keyword called “var”. Var allows you to declare a new variable, whose type is implicitly inferred from the expression used to initialize the variable.
Syntax: var i=1;
The preceding line initializes the variable i to value 1 and gives it the type of integer. It is not an object or variant.
Anonymous types:
C# 3.0 gives you the flexibility to create an instance of a class without having to write code for the class beforehand. So, you now can write code as shown below:
new {StudentID=1, StudentName=”XYZ”, Marks=90}
The preceding line of code, with the help of the “new” keyword, gives you a new type that has three properties: StudentID, StudentName, and Marks. Behind the scenes, the C# compiler would create a class that looks as follows:
class __Anonymous1
{
private int _StudentID = 1;
private string _StudentName = “XYZ”;
private int _Marks = 64;
public int StudentID {get { return _StudentID; } set { _StudentID = value; }}
public string StudentName {get { return _StudentName; } set { _StudentName = value; }}
public int Marks {get { return _Marks; } set { _Marks = value; }}
}

Extension methods:

Extension methods enable you to extend various types with additional static
methods. Extension methods can be declared only in static classes and are identified by
the keyword “this” as a modifier on the first parameter of the method.

The following is an example of a valid extension method:
public static int ToInt32(this string s)
{
return Convert.ToInt32(s) ;
}
Object and collection initializers:
C# 3.0 is expected to allow you to include an initializer that specifies the initial values of the members of a newly created object or collection. This enables you to combine declaration and initialization in one step.
For instance, if you defined a CoOrdinate class as follows:
public class CoOrdinate
{
public int x;
public int y;
}

You then could declare and initialize a CoOrdinate object using an object initializer, like this:

var myCoOrd = new CoOrdinate{ x = 0, y= 0} ;
You should easily be able to give values to collections in a rather concise and compact manner in C# 3.0.
In C# 2.0 Code we write :

List<string> animals = new List<string>();

animals.Add(“monkey”);
animals.Add(“donkey”);
animals.Add(“cow”);
animals.Add(“dog”);
animals.Add(“cat”);

It can be written in  C# 3.0 shortened to simply.
List<string> animals = new List<string> {“monkey”, “donkey”, “cow”, “dog”, “cat” } ;
Lambda expressions:
C#(1.x) allowed you to write code blocks in methods, which you could invoke easily using delegates.Delegates are definitely useful, and they are used throughout the framework, but in many instances you had to declare a method or a class just to use one. Thus, to give you an easier and more concise way of writing code, C# 2.0 allowed you to replace standard calls to delegates with anonymous methods.
In C# 2.0, using anonymous methods, you could rewrite the code as follows:
class Program
{
delegate void DemoDelegate();
static void Main(string[] args)
{
DemoDelegate myDelegate = delegate()
{
Console.Writeline(“Hiya!!”);
};
myDelegate();
}
}
The above code can now be replaced with the following code in C# 3.0:
class Program
{
delegate void DemoDelegate();
static void Main(string[] args)
{
DemoDelegate myDelegate = () => Console.WriteLine(“Hiya!!”) ;
myDelegate();
}
}

Reference Site: http://www.developer.com/net/csharp/article.php/10918_3561756_1


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Code Sample to Upload file to FTP Server

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check out below code to upload file to FTP Server:

 

/// <summary>
/// Code to upload file to FTP Server
/// </summary>
/// <param name=”strFilePath”>Complete physical path of the file to be uploaded</param>
/// <param name=”strFTPPath”>FTP Path</param>
/// <param name=”strUserName”>FTP User account name</param>
/// <param name=”strPassword”>FTP User password</param>
/// <returns>Boolean value based on result</returns>
private bool UploadToFTP(string strFilePath, string strFTPPath, string strUserName, string strPassword)
{
        try
        {
                //Create a FTP Request Object and Specfiy a Complete Path
                string strFileName = strFilePath.Substring(strFilePath.LastIndexOf(“\”) + 1);
                FtpWebRequest reqObj = (FtpWebRequest)WebRequest.Create(strFTPPath + @”/” + strFileName);
                //Call A FileUpload Method of FTP Request Object
                reqObj.Method = WebRequestMethods.Ftp.UploadFile;
                //If you want to access Resourse Protected You need to give User Name and PWD
                reqObj.Credentials = new NetworkCredential(strUserName, strPassword);
                // Copy the contents of the file to the request stream.
                StreamReader sourceStream = new StreamReader(strFilePath);
                byte[] fileContents = Encoding.UTF8.GetBytes(sourceStream.ReadToEnd());
                sourceStream.Close();
                reqObj.ContentLength = fileContents.Length;
                Stream requestStream = reqObj.GetRequestStream();
                requestStream.Write(fileContents, 0, fileContents.Length);
                requestStream.Close();
                FtpWebResponse response = (FtpWebResponse)reqObj.GetResponse();
                response.Close();
        }
        catch (Exception Ex)
        {       // report error
                throw Ex;
        }
        return true;
}


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Icon in the Address bar Textbox in Browsers

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(Short Cut) Icon in the Address bar Textbox in Browsers

You have to insert this line after the <head> tag in your html / ASPX / Master Page.

<link rel=”shortcut icon” href=”images/MyComp.ico”>

Make sure the image is file type .ico (for icon). Also, after inserting this line, the image may not appear immediately. So, Try to Refresh the page.

Here’s an article for that:

How to Add a Shortcut Icon to a Web Page

 

Other way to achieve the same thing is as follows

 

       Save the icon with the default file name of favicon.ico to the root directory of your domain—for example, www.microsoft.com/favicon.ico. The first time a user visits your Web page, Internet Explorer automatically searches for this file and places the icon in the address bar, next to all favorites linking to your site, and on page tabs. In Internet Explorer 5 and Internet Explorer 6, the icon will appears only after a user adds the site to the Favorites menu.

 

You can use either method, or both. However, if you use the First method, whichever icon you point to in the link tag on each page will be displayed instead of the default favicon.ico file at the root of your domain.


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Convert Date Formats :

 

//For ex., Convert MM/dd/YYYY to dd/MM/yyyy

string date = “03/27/2008”; //format is MM/dd/yyyy

DateTimeFormatInfo dateTimeFormatterProvider = DateTimeFormatInfo.CurrentInfo.Clone() as DateTimeFormatInfo;

dateTimeFormatterProvider.ShortDatePattern = “MM/dd/yyyy”; //source date format

DateTime dateTime = DateTime.Parse(date, dateTimeFormatterProvider);

string formatted = dateTime.ToString(“dd/MM/yyyy”); //write the format in which you want the date tobe converted

Response.Write(“<br />” + formatted);


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Maintaining Fck editor value during postbacks

Here is the code to maintain value of FckEditor value during postbacks,

 

Write in Page_Load event,

 

Page.ClientScript.RegisterOnSubmitStatement(

fckContentPage.GetType(),

“fckContentPage”,

“FCKeditorAPI.GetInstance(‘” + fckContentPage.ClientID + “‘).UpdateLinkedField();”);

 

Here fckContentPage is ID of FckEditor


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