ROW_NUMBER -Sqlserver

This is a special keyword used for generate "Sequential No'   on a row within result set. Sequential no start from 1 for first row, second row no is 2 in each partition. Usually used in Select Statement.

ROW_NUMBER () OVER ( [ <partition_by_clause> ] <order_by_clause> ) 

Arguments:

ROW_NUMBER has Two Arguments are 
1. Partition_by_clause and
2.  order_by_clause 

ROW_NUMBER() with PARTITION :

Partition BY Clause to generate Sequence No to separate of query result and Order By works on over clause for order the results.

SELECT  ROW_NUMBER() OVER(PARTITION BY IsApproved ORDER BY Id DESC ) AS SL_NO ,[Name]
      ,[Address]      ,[Telephone]  ,[IsApproved]
      FROM [RemitERP].[dbo].[Agm_Agent] 
WHERE IsApproved IS NOT NULL

ROW_NUMBER()  Only ORDER BY :

Order by clause works all result of the query and generate sequence No.

 SELECT  
      ROW_NUMBER() OVER( ORDER BY Id DESC ) AS SL_NO ,[Name]
      ,[Address]      ,[Telephone]  ,[IsApproved]
      FROM [Agm_Agent] 
WHERE IsApproved IS NOT NULL