Re: syntax for updating an aliased table

Andy Chambers wrote:
> I'm confused about the correct syntax for updating an aliased table. I want
> to update triple from triple_updates
> where the data is different and tried to use the following....
>
> update triple old
> set
> old.obln = new.obln, old.ointv = new.ointv,
> old.otime = new.otime, old.oflt = new.oflt, old.ostr = new.ostr,
> old.oint = new.oint, old.oda = new.oda, old.uasid = new.uasid
> from triple_update as new
> where (old.s = new.s and
> old.g = new.g) and
> ( old.obln <> new.obln or old.ointv <>
> new.ointv or old.otime <> new.otime or old.oflt <> new.oflt or old.ostr
> <> new.ostr or old.oint <> new.oint or old.oda <> new.oda or old.uasid <>
> new.uasid)
>
>
> ...but postgres complains about not having column "old" in the triple table.
> Putting an "as" between triple and old on the first line didn't make any
> difference. If
> I leave out the old alias, it complains about the columns being ambiguous.
> How should the query above be changed to be syntactically correct?

Don't use the table alias (or name for that matter) on the left-hand side of
the assignments, so:

update triple old
set obln = new.obln,
ointv = new.ointv,
...
from triple_update as new
where (old.s = new.s and old.g = new.g) and ...

The update statement already unambiguously defines what table is being updated
and the target columns are all that are necessary in the assignments.

HTH

Bosco.