Update top N values using PostgreSQL

Question

I want to update the top 10 values of a column in table. I have three columns; id, account and accountrank. To get the top 10 values I can

Answer 1

Sure, you can use your select statement in a subquery. Generating the rank-order isn't trivial, but here's at least one way to do it. I haven't tested this, but off the top of my head:

update accountrecords
set accountrank =
    (select count(*) + 1 from accountrecords r where r.account > account)
where id in (select id from accountrecords order by account desc limit 10);

This has the quirk that if two records have the same value for account, then they will get the same rank. You could consider that a feature... :-)