dense_rank ranking window function
Applies to: 
Databricks SQL Databricks Runtime
Returns the rank of a value compared to all values in the partition.
Syntax
dense_rank()
Arguments
This function takes no arguments.
Returns
An INTEGER.
The OVER clause of the window function must include an ORDER BY clause.
Unlike the function rank ranking window function, dense_rank will not produce gaps in the ranking sequence.
Unlike row_number ranking window function, dense_rank does not break ties.
If the order is not unique the duplicates share the same relative later position.
Examples
SQL
> SELECT a,
b,
dense_rank() OVER(PARTITION BY a ORDER BY b),
rank() OVER(PARTITION BY a ORDER BY b),
row_number() OVER(PARTITION BY a ORDER BY b)
FROM VALUES ('A1', 2), ('A1', 1), ('A2', 3), ('A1', 1) tab(a, b);
A1 1 1 1 1
A1 1 1 1 2
A1 2 2 3 3
A2 3 1 1 1