CTE ( Common Table expression ) in SQL Server

-
Its very new concept for me, heard from Mr.Vinayak Sir.
Thanks to them.

CTE (Common Table Expression ) is nothing but return same result as SELECT query will do with the help of JOINS,UNION etc.

It allows you to define the subquery at once, name it using an alias and later call the same data using the alias just like what you do with a normal table.

Take a look at following difference between plain query with join and CTE query

Plain SQL query :

Its plain query.




CTE query :

Using CTE syntax/format , we define query as follows,

Syntax :

With [table_aliesname] ( userDefinedColumn1,userDefinedColumn2,userdefinedcolumnN )
As
(
[Plain SQL select query.]
)
-- If you want to join more table only need to give ',' comma for closing round bracket and continue as same as T2 table in Examle

 Regards,
 Nihar Kulkarni  :) :)
 


 

Comments

Post a Comment

Popular posts from this blog

File operations in C# (.net)

-
Here we are performing some basic file operations which widely needed in applications. ASPX :     <div>         <asp:Button ID="Button1" runat="server" Text="CLick" onclick="Button1_Click" />         <asp:FileUpload ID="FileUpload1" runat="server" /><br /><br />          </div> C# :        using System.IO;        using System.Text;         protected void Button1_Click(object sender, EventArgs e)         {             string path = @"E:\MVC Application Demos\ABC.txt";            // File Path taken             string name = FileUpload1.FileName.ToString();                // Here we get File Name only             string pa...
Read more

Add Serial no in crystal report without coding

-
Image
Adding a serial number in grouping without any code. I have placed the step by step screenshots which will explain easily how to do it.   1) Add a new field in Running Total Fields in Field Explorer   Give a proper name to your Running total name. For example I have choosen here RTotal0. Now categorize based on which field in database you want to summarize it. Next is as we want serial number select count. If you want your serial number to start again from the start when the value in the group changes then select on change of group and specify the grouping name else keep the default value.   Smaple Preview of the Design View of Report where I Have added SRNo column at the start in grouping section.  
Read more

How to get top " n " number of rows from table

-
Suppose you want top n values from table , so execute following query with replacement of following item as mention below : 1 )  Replace your our tablename with [table_name] 2 )  Replace your "n" with row numbers  (how many rows you want ) [ Note :  You can do multiply and division operations also ] Query for Top rows : SELECT MainSQL .* FROM ( SELECT t .*, ROW_NUMBER () OVER ( ORDER BY 1 ) Row_Number , COUNT ( 1 ) OVER ( ORDER BY 1 RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING ) Row_Count FROM (SELECT * FROM [table_name] )  t ORDER BY 1 ) MainSQL WHERE Row_Number >= 1 AND Row_Number < ( 1 + 2 ) ORDER BY Row_Number ; Query for Bottom  rows : SELECT MainSQL .* FROM ( SELECT t .*, ROW_NUMBER () OVER ( ORDER BY 1 ) Row_Number , COUNT ( 1 ) OVER ( ORDER BY 1 RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING ) Row_C...
Read more