RANK function

You use the RANK function to return the rank of the value in the current row as compared to the value in other rows. The rank of a value reflects the order in which it would appear if the list of values was sorted.

When using the RANK function, the rank is calculated for the expression specified in the window's ORDER BY clause. If the ORDER BY clause includes multiple expressions, the second and subsequent expressions are used to break ties if the first expression has the same value in adjacent rows. NULL values are sorted before any other value (in ascending sequence).

 Example 1
 Example 2
 Example 3