Question

I made a simple query that checks for how much money a customer has bought singles:

SELECT k.voornaam || ' ' || k.familienaam as "Naam", sum( b.aantal * s.prijs) as "Omzet"  

from bestellingen b 
left join klanten k on k.klantid = b.klantid
left join singles s on s.singleid = b.singleid
where b.klantid = 12
group by k.voornaam,k.familienaam

this returns :

but I also need a third column named type customer

>

I have to find how good this revenue is in comparison with all the other customers

• the top 25% = I have to return ‘very good’
• 25 to 50% = return ‘good’
• 50 to 75% = return ‘average’
• 75% to 100% = ‘bad’

So I need the calculate the revenue for each customer and see how it compares to them.

How do i do this?
I can also use PL/SQL if this is better fit for this job as I am building an oracle project (apex).

thx 🙂

Answer 1

I assume Oracle Apex has the functionality underlying Oracle. You can do this with the percentile analytic function:

with t as (
     SELECT k.voornaam || ' ' || k.familienaam as "Naam",
            sum( b.aantal * s.prijs) as "Omzet"
     from bestellingen b left join
          klanten k
          on k.klantid = b.klantid left join
          singles s
          on s.singleid = b.singleid
     where b.klantid = 12
     group by k.voornaam,k.familienaam 
    )
 select t.*,
        (case when percentile between 0 and 0.25 then 'VeryGood'
              when percentile between 0.25 and 0.5 then 'Good'
              when percentile between 0.5 and 0.75 then 'Average'
              else 'Bad'
         end) as CustGrp
 from (select t.*,
              percent_rank() over (order by omzet desc) as percentile
       from t
      ) t

I’m assuming “omzet” means revenue.