The WHERE clause must be satisfied or surely there would be no results at all?
As for optimising, that is left as homework... Seriously, you might find some info by googling 'SQL optimise left join', quite a few results but a bit heavy for me. Sorry but it was a stretch coming up with the query. Gary -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to weewx-user+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
