Am Freitag, 5. Oktober 2001 14:30 schrieb Morgan Curley: > just get rid of the serial_id in person2adress -- there is no > reason for it. Make the pk of that table a composite --> person_id, > address_id <-- that way you have added some additional integrity to > your structure. Only one record can exist ffor a given person at a > given address. However any person can have any number of address > and any address can have any number of people living at it.
ok fine, i understood it after i figured out what pk means :-) but how do i reach my goal. It should not be allowed to have a person without any address?? janning > At 12:39 PM 10/5/2001 +0200, Janning Vygen wrote: > >create table person ( > > id serial, > > name text > >); > > > >create table address ( > > id serial, > > street text > > ... > >); > > > >create table person2adress ( > > id serial, > > person_id integer not null references person(id), > > address_id integer not null references address(id), > >); > > > >than i can select all adresses from one person with id =1 with > >select street > >from address > >where id = > > ( > > select adress_id > > from person2adress > > where person_id = 1 > > ); > > > >ok so far so good. but you can still insert persons without any > >adress. so its a 0..n relation. But how van i achieve that you > > canīt insert any person without adress??? ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html
