sql - group by in ranges to include ranges without values

Question

Suppose a scenario similar to this question. I want to get the following results:

score range  | number of occurrences
-------------------------------------
   0         


        

Answer 1

You cannot like that, but if you add derived table with ranges things become possible:

select ranges.range, count(scores.score) as [number of occurences]
  from
  (
     select 0 minRange, 9 maxRange, '0-9' range
     union all
     select 10, 19, '10-19'
     union all
     select 20, 29, '20-29'
  ) ranges
  left join scores
    on scores.score between ranges.minRange and ranges.maxRange  
 group by ranges.range

Not sure about syntax of postgresql though.

EDIT: Got the syntax right:

select ranges."range", count(scores.score) as "number of occurences"
  from
  (
     select 0 minRange, 9 maxRange, '0-9' "range"
     union all
     select 10, 19, '10-19'
     union all
     select 20, 29, '20-29'
  ) as ranges
  left join scores
    on scores.score between ranges.minRange and ranges.maxRange  
 group by ranges.range