RANK function [Analytical]

Ranks items in a group.

RANK () OVER ( ORDER BY expression [ ASC | DESC ] )

The following statement illustrates the use of the RANK function:

SELECT s_suppkey, SUM(s_acctBal) AS sum_acctBal,
RANK() OVER ( ORDER BY SUM(s_acctBal) DESC )
AS rank_all FROM supplier GROUP BY s_suppkey;

s_suppkey        sum_acctBal       rank_all
supplier#011     200000            1
supplier#002     200000            1
supplier#013     123000            3
supplier#004     110000            4
supplier#035     110000            4
supplier#006     50000             6
supplier#021     10000             7

RANK is a rank analytical function. The rank of row R is defined as the number of rows that precede R and are not peers of R. If two or more rows are not distinct within the groups specified in the OVER clause or distinct over the entire result set, then there are one or more gaps in the sequential rank numbering. The difference between RANK and DENSE_RANK is that DENSE_RANK leaves no gap in the ranking sequence when there is a tie. RANK leaves a gap when there is a tie.

RANK requires an OVER (ORDER BY) clause. The ORDER BY clause specifies the parameter on which ranking is performed and the order in which the rows are sorted in each group. This ORDER BY clause is used only within the OVER clause and is not an ORDER BY for the SELECT. No aggregation functions in the rank query are allowed to specify DISTINCT.

The OVER clause indicates that the function operates on a query result set. The result set is the rows that are returned after the FROM, WHERE, GROUP BY, and HAVING clauses have all been evaluated. The OVER clause defines the data set of the rows to include in the computation of the rank analytical function.

The ASC or DESC parameter specifies the ordering sequence ascending or descending. Ascending order is the default.

RANK is allowed only in the select list of a SELECT or INSERT statement or in the ORDER BY clause of the SELECT statement. RANK can be in a view or a union. The RANK function cannot be used in a subquery, a HAVING clause, or in the select list of an UPDATE or DELETE statement. Only one rank analytical function is allowed per query.