it's explained pretty well on the book http://web2py.com/books/default/chapter/29/06/the-database-abstraction-layer#belongs
let me know if something is not clear Il giorno mercoledì 25 settembre 2013 07:11:27 UTC+2, step ha scritto: > > Niphlod, can you please explain why you're using method _select instead of > select in your code below? In there no need to connect to SQL to set > all_courses? > > On Tuesday, September 24, 2013 3:35:34 PM UTC+2, Niphlod wrote: >> >> 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. >>> >>> >>> -- Resources: - http://web2py.com - http://web2py.com/book (Documentation) - http://github.com/web2py/web2py (Source code) - https://code.google.com/p/web2py/issues/list (Report Issues) --- You received this message because you are subscribed to the Google Groups "web2py-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to web2py+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.