In SQL, how can you “group by” in ranges?

Question

Suppose I have a table with a numeric column (lets call it \"score\").

I\'d like to generate a table of counts, that shows how many times scores appeared in each ran

Answer 1

In postgres (where || is the string concatenation operator):

select (score/10)*10 || '-' || (score/10)*10+9 as scorerange, count(*)
from scores
group by score/10
order by 1

gives:

 scorerange | count 
------------+-------
 0-9        |    11
 10-19      |    14
 20-29      |     3
 30-39      |     2