Query to rank rows in groups

Question

I\'m using Apache Derby 10.10.

I have a list of participants and would like to calculate their rank in their country, like this:

|        Country |           


        

Answer 1

Consider a non-windows function SQL query that uses a correlated aggregate count subquery. Because the group column (Country.name) is not in same table as the rank criteria (Participant.points), we need to run same joins in the subquery but rename table aliases to properly compare inner and outer queries.

Now of course, in a perfect world that would be it but we must now account for tied points. Therefore, another very similar subquery (for tie breaker) is used to be added to first subquery. This second nested query matches inner and outer query's Country.name and Participant.points but ranks by alphabetical order of Participant.name.

SELECT
    Country.name AS Country,
    Participant.name AS Participant,
    Participant.points,
    (SELECT Count(*) + 1
       FROM Country subC
      INNER JOIN Team subT
              ON subC.id = subT.country_id
      INNER JOIN Participant subP
              ON subT.id = subP.team_id
      WHERE subC.name = Country.name
        AND subP.points < Participant.points) 

     +

    (SELECT Count(*)
       FROM Country subC
      INNER JOIN Team subT
              ON subC.id = subT.country_id
      INNER JOIN Participant subP
              ON subT.id = subP.team_id
      WHERE subC.name = Country.name
        AND subP.points = Participant.points
        AND subP.name < Participant.name)  As country_rank

FROM Country
INNER JOIN Team
        ON Country.id = Team.country_id
INNER JOIN Participant
        ON Team.id = Participant.team_id
ORDER BY Country.name, Participant.points;