Rank vs Dense_Rank

1. Rank(), Dense_Rank() are OLAP Functions
   
2. They are used to find ranks for a table based on certain business logic.
   
3. Syntaxes:
   
   1. Rank() over ( expr );
      
   2. Dense-Rank() over ( expr );
4. The difference between rank and dense rank is that,
   
   
   
   Rank : Generate gap when there are same ranks.
   
   Dense_Rank: Doesn't generate a gap when there are same ranks.
5. These functions must not be used in where clause.