postgres column alias problem

Question

As a newbie to Postgresql (I\'m moving over because I\'m moving my site to heroku who only support it, I\'m having to refactor some of my queries and code. Here\'s a problem

Answer 1

In PostgreSQL you can not use expression with an alias in order by. Only plain aliases work there. Your query should look like this:

   select distinct 
          l2.*, 
          l.user_id as l_user_id, 
          l.geopoint_id as l_geopoint_id 
     from locations l 
left join locations l2 on l.geopoint_id = l2.geopoint_id 
    where l.user_id = 8 
 order by l2.geopoint_id, l.user_id = l2.user_id desc;

I assume you mean that l2.user_id=l.user_id ought to go first.

This is relevant message on PostgreSQL-general mailing list. The following is in the documentation of ORDER BY clause:

Each expression can be the name or ordinal number of an output column (SELECT list item), or it can be an arbitrary expression formed from input-column values.

So no aliases when expression used.