understanding difference between rank, dense rank and row number

Author: techysanoj

rank_dense_rank_row_number_difference.sql

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+-- talking about the difference
+-- firstly talk about similarities
+
+
+-- when there are no duplicates in the data according to the order by clause column
+-- then each will give integer numbering starting with 1 and goes till the last row number
+
+-- but if there are duplicates in the data according to the order by clause column
+-- then 
+-- row_number will act as same - 1, 2, 3, 4, 5
+-- rank : 1, 1, 3, 4, 5 - it will skip the rank for the duplicate entry and then start with next rank
+-- dense_rank: 1, 1, 2, 3, 4- it will not skip the rank either it will give next rank to the other row when there are ties
+