OK, we’ve thought of another possibility, still seems a bodge though:
Select case when exists(Select vat_rate from vatrates where vat_code=’1’ and vat_date<=’2014-08-01’)
Then (Select vat_rate from vatrates where vat_code=’1’ and vat_date<=’2014-08-01’ order by vat_date desc limit 1)
Else (select 0 as vat_rate from vatrates limit 1)
From: pgsql-novice-owner@postgresql.org [mailto:pgsql-novice-owner@postgresql.org] On Behalf Of Rob - TEAM Systems Ltd
Sent: 22 August 2014 12:19
To: pgsql-novice@postgresql.org
Subject: [NOVICE] How to return a default value if no result
I want my query to return at least one row with a default result even if there are no matches in the database.
As a simple example, getting the valid VAT rate for a transaction date and VAT code:
Select vat_rate from vatrates where vat_code=’1’ and vat_date<=’2014-08-01’ order by vat_date desc limit 1
This is fine as long as there is a match. If there are no matches, I’d like it to return a default (0) rather than no result.
I could make sure there is always a result by having a UNION with a hard-coded record, but this doesn’t let me order by a field not in the result.
In this example I could just make sure there is a dummy row in the table with a very old date and do something like this:
Select vat_rate from vatrates where (vat_code=’1’ or vat_code=’DUMMY’) and vat_date<=’2014-08-01’ order by vat_date desc limit 1
But it seems like a bodge to me.
Is there a nice way of forcing a default result somehow?
Thanks,
Rob