you can do that with
all_courses = db(db.courses.id>0)._select(db.courses.memberid)
all_members_not_in_courses = db(~db.members.id.belongs(all_courses))
you can eventually throw in a distinct on db.courses.memberid if the number
of courses rows is plenty.
Il giorno martedì 24 settembre 2013 12:16:52 UTC+2, Michael Hall ha scritto:
>
> I am not the most awesome SQL person and as such I am having trouble
> constructing a query I need.
>
> I have two tables in a database called "old". The parent table is called
> "members" and there is a child table called "courses".
>
> #--------
> old.define_table('members',
> Field('id'),
> Field('profile_id','string'),
> Field('title','string'),
> Field('firstname','string'),
> Field('surname','string'),
> Field('memberlevel','string'),
> Field('lawfirm','string'),
> Field('registerdate','date'),
> Field('expirydate','date'),
> Field('email','string'),
> Field('telno','string'),
> Field('address1','string'),
> Field('address2','string'),
> Field('address3','string'),
> Field('town','string'),
> Field('county','string'),
> Field('postcode','string'),
> Field('country','string'),
> Field('notes','text'),
> Field('memberstatus','string'),
> migrate=False)
>
> old.define_table('courses',
> Field('memberid',type='reference members',),
> Field('profile_id','string'),
> Field('course','string'),
> Field('enroldate','string'),
> migrate=False)
>
> I would like to select all records in the members table that are not
> referenced by records in the courses table. I suppose it could be described
> as the opposite of a join as I only want to select members that do not have
> courses attached to them.
>
> Any help would be appreciated.
>
>
>
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