select distinct o.bid, organisation, posttown, replace(case when phone ='' then null else trim(phone) end, ' ', ''), phone, o.active, website, email, (select count(*) from notes as n where n.bid = o.bid) as nn from organisations as o right join notes as n on o.bid = n.bid where true order by replace(case when phone ='' then null else trim(phone) end, ' ', '') nulls last ;
This does not work:
select distinct (o.bid), organisation, posttown, replace(case when postcode ='' then null else trim(postcode) end, ' ', '') as pc, phone, o.active, website, email, (select count(*) from notes as n where n.bid = o.bid) as nn from organisations as o right join notes as n on o.bid = n.bid where true order by replace(case when phone ='' then null else trim(phone) end, ' ', '') nulls last ; ERROR: for SELECT DISTINCT, ORDER BY expressions must appear in select list LINE 1: ...n notes as n on o.bid = n.bid where true order by replace(ca...
The documentation does not explain the restriction, nor that, or why, you cannot use 'as' to rename the field and then cite the renamed version.
Let me get some clarity now since my first reply saw an "ON" clause where there isn't one...
What was the point of adding parens around o.bid in the second query? (I assumed it was to do DISTINCT ON but you didn't add the word ON)
Why did you change replace(case when phone...) in the first query with replace (case when postcode...) in the second query - but only in the select-list? (phone no longer exists in the select-list and thus you get the error.)
The following works just fine with an alias in the ORDER BY:
WITH vals (v,t,o) AS ( VALUES (1,'a',10),(2,'c',20),(3,'d',30),(3,'b',40),(4,'e',50) )
Adding "o" to the ORDER BY provokes the error you have been seeing.
Tom has explained why this is the case. In short, DISTINCT seems to effectively remove the ability to specify "arbitrary expressions from input column values" in the ORDER BY - though you can still specify non-arbitrary expressions, as long as they are the same expressions that are used in the select-list.
