Well, if you're going to write some queries, let's ask what's the point? While that is normally a snarky comment, in this case it might be worthwhile figuring out what data is of interest so that one query will generate a spreadsheet that folks can play with to their heart's content. I think I would want user name, join date, date of first post, date of most recent post and date of most recent visit. We can discuss whether banned or deleted accounts should be included. I don't care about post count particularly but it might be more useful to filter on "# posts > 0".
It also might be time to revive the idea of hosting spreadsheets at GAD.net. I can imagine a web form that generates and runs a query and the user can download the results as a csv or tab-delimited file. Maybe run against a sanitized, cleaned up, read only copy of the database? You don't need me to tell you how ;-)