Query question

Hi,

I am new to Postgres and am trying to write a query like the one below
(without any luck)

SELECT col_speed, col_time, (col_speed / col_time) AS distance

FROM speed_ratings

HAVING distance > ?

ORDER BY distance

In other words, I want to filter on a calculated column. But I get an
error that column distance is not defined

column "distance" does not exist at character 272

Interestingly if I remove the filter (HAVING distance > ?), the query
works. So I can sort on distance but not filter.

I have tried substituting the HAVING clause with a WHERE clause as well
with no luck.

I have also added a GROUP BY clause with the HAVING as well with no
luck.

Any ideas?

Thanks

Sid