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.
Morgan At 12:39 PM 10/5/2001 +0200, Janning Vygen wrote: >Hi, > >i create n to n relations like this, right? > >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??? > >thanks in advance >janning > >---------------------------(end of broadcast)--------------------------- >TIP 4: Don't 'kill -9' the postmaster ------------- Morgan Curley Partner, e4media [EMAIL PROTECTED] 917 751 8328 http://www.e4media.com ------------------------- ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html
