On 20 Nov 2017, at 11:09am, x <tam118...@hotmail.com> wrote:
> explain > select ColA from TblA > left join TblB using (ColB) > left join TblC using (ColC) > left join TblD using (ColD) > where ColBX=?; > > there will be no trace of TblC or TblD as they're redundant. Although you have not asked for columns from the table TblC, you have specified the lookup. Perhaps you want to check that an appropriate row appears in TblC, and get an error message otherwise. (Or should SQL return NIL ?) There is an optimization opportunity for SQLite. Maybe it should check to see that a JOIN is needed before it does it. But at the moment this command is just a little slower than it should be, not exactly wrong. Simon. _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
