DQL Commands in SQL Server .

                                                        Data Query Language (DQL)

                                                                               

In general , in any language we can retrieve the data from the existing table totally in 3 ways

                                                * Selection

                                                * Projection

                                                * Joins

SELECT :

                   * We can retrieve the records from 1/more existing tables.

                   * With this command we can retrieve all the records or specific records from the tables.

Syntax : 

      SELECT CN1

      ,CN2

      ,----- ,CNn [(*)]

      FROM < TableName >

      WHERE < Condition >

      GROUP BY < COLUMN - names >

      HAVING < condition >

      ORDER BY < C.N > [asc/desc]

Projection :

  * Retrieving data from specific columns is known as Projection

            Syntax :     Select CN1,CN2 --------- CNn from <T.N>

                

                               *  Represents all columns

Note:

                * In SQL Server , by default all rows selected , if you want to select particular  rows you                        need to use where clause .

                * In a query the execution process is from left to right .

                * In a table values will be modified from top to bottom .