I see, thank you for pointing out. I wanted to use it on table with conditional relations with 3 different child tables. Though I could use a trick and fit data selection into one query, efficiently. Alas I am forced to stick to 2 queries.
Thank you! 8 February 2016, 12:08:26, by "Clemens Ladisch" <clemens at ladisch.de>: > Paul wrote: > > I am curious what is a particular reason that aliased columns in a query > > not visible to sub-queries? > > Because the SQL standard says so. > > > Of course it is possible to duplicate expression in sub-query ... > > But this would not be as efficient as to access result of already evaluated > > expression. > > An alias refers not to an expression's value but to the expression > itself, so it would not be any more efficient. (SQLite's optimizer > typically is not smart enough to detect and remove the duplication.) > > > As a workaround, you have to move the expression into a subquery in > the FROM clause: > > SELECT super_id, > (SELECT qux FROM baz WHERE id = super_id) > FROM (SELECT id as super_id FROM foo); > > > Regards, > Clemens > _______________________________________________ > sqlite-users mailing list > sqlite-users at mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
