Re: [GENERAL] two questions

> I am having two questions about psql:
>
> 1. How to define a relation with an attribute which takes set values?
> Not really sure what you mean....
>
> eg. I would like to define a table like
> create table emp (name text, tele Set(string)); -- it does
> not work
> One tuple may look like 'Jerry', {83023381,83023800}
> I can not use array since an array is not a set.
>
> 2. How to populate instances to a table referring another table? An
> example:
> Create table CITIES (name text, population float);
> Insert into cities values ('Adelaide', 100.0);
> Create table people(name text, live_in CITIES);
> How to insert a tuple into people saying that 'Jerry' lives in
> Adelaide?
> I can not use
> INSERT INTO people('Jerry', 'Adelaide');
> since live_in is not a string, it is a table named CITIES
> I am trying to use object reference of OR. Thus a reference path
> can be formed.
>
> Jerry Liu, Australia

The usual approach is to use two tables.

create table cities (name text, population float);
create table people (name text, city_name text);
insert into cities values ('Adelaide', 100.0);
insert into people values ('Jerry', 'Adelaide');
update cities set population = population + 1 where name = 'Adelaide';