Hello, I'm new to SQL and MySQL, I'm developing a web application (php) and I need
some tables relationed between them with a foreing key. The idea is the following
create table persons (
cid smallint auto_increment not null unique,
name varchar(30),
alias varchar(10),
primary key (cid));
create table phones(
pid smallint auto_increment not null unique,
cid smallint not null,
phone varchar(10),
obs varchar(40),
primary key (pid));
There are many other tables like phones and I will need to do with them the same
thinks.
The questions are the followings:
- How do I preserve integrity? I mean, I don't want to have phones without persons, so
when I delete a person I want to make a cascade erase.
- When I do a:
select * from persons left join phones using (cid);
I get as many rows as phones have this person, is there any way to make a query that
returns a single row with all the information.
Those are the first, hope can you help me.
Greeting,
Jorge Calas
Havana University.
