Difference between row_number(), rank() and dense_rank()

  

      Row_number() -> Used for generating serial number

                                           it gives unique value to each row

• RANK() ---->gives  the same row number to the same value, leaving "holes"
• DENSE_RANK() --->will assign consecutive ranks to the values in the set (so there will be no gaps between the integer ranking values in the case of a tie).