Oracle: how to “group by” over a range?

Question

If I have a table like this:

pkey   age
----   ---
   1     8
   2     5
   3    12
   4    12
   5    22

I can \"group by\" to get a count

Answer 1

I had to get a count of samples by day. Inspired by @Clarkey I used TO_CHAR to extract the date of sample from the timestamp to an ISO-8601 date format and used that in the GROUP BY and ORDER BY clauses. (Further inspired, I also post it here in case it is useful to others.)

SELECT 
  TO_CHAR(X.TS_TIMESTAMP, 'YYYY-MM-DD') AS TS_DAY, 
  COUNT(*) 
FROM   
  TABLE X
GROUP BY
  TO_CHAR(X.TS_TIMESTAMP, 'YYYY-MM-DD')
ORDER BY
  TO_CHAR(X.TS_TIMESTAMP, 'YYYY-MM-DD') ASC
/