On Mon, 2010-05-17 at 15:02 +0200, Vivien Malerba wrote: > On 17 May 2010 14:53, Murray Cumming <[email protected]> wrote: > > On Mon, 2010-05-17 at 14:43 +0200, Vivien Malerba wrote: > >> On 17 May 2010 14:39, Murray Cumming <[email protected]> wrote: > >> > On Mon, 2010-05-17 at 14:20 +0200, Vivien Malerba wrote: > >> >> On 17 May 2010 10:07, Murray Cumming <[email protected]> wrote: > >> >> > In Glom, I use the AS keyword with JOINS, to allow multiple joins with > >> >> > the same table. A simple case looks like this, though it's unnecessary > >> >> > in this particular example: > >> >> > > >> >> > SELECT "albums"."album_id", "albums"."name", "albums"."artist_id", > >> >> > "relationship_artist"."name", > >> >> > FROM "albums" > >> >> > LEFT JOIN "artists" > >> >> > AS "relationship_artist" > >> >> > ON ("albums"."artist_id" = "relationship_artist"."artist_id") > >> >> > WHERE "albums"."album_id" = 123 > >> >> > > >> >> > (That might be an "alias", but I don't know if that's the right > >> >> > terminology.) > >> >> > > >> >> > But I don't see how to do that with > >> >> > gda_sql_builder_select_join_targets() > >> >> > http://library.gnome.org/devel/libgda/unstable/GdaSqlBuilder.html#gda-sql-builder-select-join-targets > >> >> > > >> >> > >> >> To do this you need to specify an alias when using the > >> >> gda_sql_builder_select_add_target*() methods. > >> > > >> > But that's for adding table targts, right? How would it know which join > >> > the alias name is for? > >> > > >> > >> The alias is for a target (table or sub select), not for a join: you > >> don't need to name joins as they are never referenced anywhere else in > >> the SQL statement, you can name targets if necessary. > > > > In my example, the join name is mentioned in the list of fields. For > > instance, relationship_artist.name. > > > > Here's a silly example that shows the need for the name, because using > > the table name would be ambiguous: > > > > SELECT "albums"."album_id", "albums"."name", > > "albums"."artist_singer_id", "relationship_artist_singer"."name", > > "albums"."artist_drummer_id", "relationship_artist_drummer"."name", > > FROM "albums" > > LEFT JOIN "artists" > > AS "relationship_artist_singer" > > ON ("albums"."artist_singer_id" = > > "relationship_artist_singer"."artist_id") > > LEFT JOIN "artists" > > AS "relationship_artist_drummer" > > ON ("albums"."artist_drummer_id" = > > "relationship_artist_drummer"."artist_id") > > WHERE "albums"."album_id" = 123 > > > > This example illustrates why you need to be able to set targets' > aliases. In this example you have the following targets: > A: "albums" > B: "artists" with the "relationship_artist_singer" alias > C: "artists" with the "relationship_artist_drummer" alias > > and you reference the targets using their alias in the join condition > and in the list of fields to be selected. > > and 2 joins (joinning conditions not mentionned here): > A <--> B > A <--> C > > the joins themselves are never referenced anywhere in the statement, > so they are not named.
So the SQL statement would/could look different? -- [email protected] www.murrayc.com www.openismus.com _______________________________________________ gnome-db-list mailing list [email protected] http://mail.gnome.org/mailman/listinfo/gnome-db-list
