Oracle三种rank的区别

rank：1 2 2 2 2 6

rank() over([partition by col1] order by col2)  

denseRank：1 2 2 2 2 3

dense_rank() over([partition by col1] order by col2)  

rowNumber：1 2 3 4 5 6

row_number() over([partition by col1] order by col2)