Обсуждение: array_agg order by

<p class="MsoNormal">Hello, <p class="MsoNormal">I am using a array_agg to get a subset of data to use in a query.<span
style="mso-spacerun:yes"> </span>However, I can’t figure out how to get the data returned in the array_agg function to
sortwith an order by function.<span style="mso-spacerun:yes">  </span>Any help would be appreciated.<span
style="mso-spacerun:yes"> </span>Here is my query as it is now.<span style="mso-spacerun:yes">  </span>I am using
postgresql8:<p class="MsoNormal"> <p class="MsoNormal">select pestproxshapes.pt_id, pestproxshapes.gid,
array_to_string(array_agg(coalesce(pestproxdata.agent|| ' | Closest Agent (km): ' || round(pestproxdata.metric1,2) || '
|Acres: ' || round(pestproxdata.metric2, 2) || ' | count: ' || pestproxdata.count || ' | yr: ' || pestproxdata.year ||
'| prob: ' || round(pestproxdata.prob,2) || ' | host: ' || pestproxdata.host, 'no agents reported within 75km')), '\n')
asAGENTS from pestproxshapes left outer join pestproxdata on pestproxshapes.pt_id=pestproxdata.pt_id where
pestproxshapes.pt_id= 8089 group by pestproxshapes.pt_id, pestproxshapes.gid;<p class="MsoNormal"> <p
class="MsoNormal">Thanks,<p class="MsoNormal">Derek 

jdmorgan <jdmorgan@unca.edu> writes:
> I am using a array_agg to get a subset of data to use in a 
> query.However, I can't figure out how to get the data returned in the 
> array_agg function to sort with an order by function.Any help would be 
> appreciated.Here is my query as it is now.I am using postgresql 8:

Well, if you were using 9.0 or later, you could do this "right":
select array_agg(foo order by bar), otherstuff from ..tables..;

You can kind of get there in older versions with a sub-select:
select array_agg(foo), otherstufffrom  (select foo, otherstuff from ..tables.. order by whatever) ss;

However that's a bit shaky because you can't do very much in the outer
query, like say grouping, without risking messing up the sort ordering.
You have to keep a close eye on the EXPLAIN output for your query to
make sure nothing re-sorts the data before it gets to the Aggregate
step.
        regards, tom lane