Order By character varying time strings?

Question

I'm querying a table and I'm trying to Order By a "time" column that has the time formatted as "1 - 2 pm", "7 - 8 am", "11 am - 12 pm", etc etc. I'm not allowed to alter this column, but I can't think of a good way to query it so that I can order it properly by asc or desc . I tried looking for the position or "am" or "pm" and using the PostgreSLQ substring method, but I'm still having trouble.

Answer 1

Add a sortby column to your query

select blah
, case when timefield = "earlier than 1am" then 1
when timefield = "1-2 am" then 2
etc
else 20 end sortby
etc
order by sortby

Answer 2

I think you can do it this way:

order by to_timestamp(time, 'HH a.m.');

Here is an example:

select time, to_timestamp(time, 'HH a.m.')
from (select '1 p.m. - 2 p.m.' as time union all
      select '9 a.m. - 10 a.m.' as time union all
      select '11 a.m. - 12 p.m.' as time
     ) t
order by to_timestamp(time, 'HH a.m.');