Mark King <fires10(at)gmail(dot)com> writes:
> I have a table with sampledate, meter1, meter2...etc
> I am trying to develop a function or query
> where:
> select sampledate, (meter1 - (select meter1 where sampledate = sampledate +
> interval '1 days')) as consumption from mytable;
> Any ideas how to make this work?
I think what you're looking for is window functions, specifically the
LEAD/LAG functions. You need Postgres >= 8.4 for those though.
regards, tom lane