Only available if arbitrary SQL is enabled (the default).

?_where=id in (1,2,3)&_where=id in (select tag_id from tags)

Allows any table (or view) page to have arbitrary additional extra_where clauses defined using the URL!

This would be extremely useful for building JavaScript applications against the Datasette API that only need on extra tiny bit of SQL but still want to benefit from other table view features like faceting.

Would be nice if this could take :named parameters and have them filled in via querystring as well.