Instance of how to use uuids on Postgres.

uuid.sql

CREATE EXTENSION IF NOT EXISTS "uuid-ossp";

select uuid_generate_v4();

SELECT uuid_in(md5(random()::text || now()::text)::cstring);

create table teste (
	id uuid not null primary key
);

insert into teste (id)values(uuid_generate_v4())
;
select * from teste;

select 
uuid_generate_v4() as bla;
union all
uuid_generate_v4() as bla;