PostgreSQL ranking and related

Question

I have a table which stores userids and their points in different categories. The number of users will keep changing. The points will also keep changing (like the points in stackoverflow). So a user who logins in will see a dashboard which says, for each of the 3 categories - You have 850 points, there are 950 users ahead of you. This is the query I have now -

WITH USERS AS (
   SELECT COUNT(*) TOT 
   FROM user_pointS
) 
SELECT ' You have ' || points_cat1 ||' points and there are '|| tot-rnk || ' ahead of you '   
FROM (
    SELECT ID,  
           points_cat1, 
           rank() OVER (ORDER BY  points_cat1 DESC ) AS RNK 
    FROM user_pointS
  ) AS RANKED, 
    USERS
WHERE ID = 10

Is there a better way (performance-wise)? I will have to repeat this for the 3 columns?

Answer 1

Well, you can do this without the CTE:

SELECT ' You have ' || points_cat1 ||' points and there are '|| tot-rnk || ' ahead of you '   
FROM (SELECT ID, points_cat1, 
              rank() OVER (ORDER BY points_cat1 DESC ) AS RNK ,
              count(*) over () as TOT
      FROM user_pointS
     ) RANKED
WHERE ID = 10;

You can do it for all three catagories at once:

SELECT ' You have ' || points_cat1 ||' points and there are '|| tot-rnk1 || ' ahead of you ',
       ' You have ' || points_cat2 ||' points and there are '|| tot-rnk2 || ' ahead of you ',
       ' You have ' || points_cat3 ||' points and there are '|| tot-rnk3 || ' ahead of you '

FROM (SELECT ID, points_cat1, points_cat2, points_cat3,
              rank() OVER (ORDER BY points_cat1 DESC ) AS RNK ,
              rank() OVER (ORDER BY points_cat2 DESC ) AS RNK1 ,
              rank() OVER (ORDER BY points_cat3 DESC ) AS RNK2 ,
              count(*) over () as TOT
      FROM user_pointS
     ) RANKED
WHERE ID = 10;

You can probably replace the tot-rnk with an inverse ranking:

 rank() OVER (ORDER BY points_cat1 ASC ) AS RNK

but you would want to test that to be sure it gives you the results you expect.