Single query SELECT propagate to childs - php

Question

i have this table structure:
id
name
email
child_id <- pointing to id from "child" table
how SELECT this table data and propagate select to all childs with a SINGLE QUERY?

Answer 1

If you assume you're working with a child table with its own name and id field, you could write...
select c.name as child_name, p.name as parent_name
from child c
join parent p
on c.id = p.child_id
I made a SQLFiddle with the following SQL:
CREATE TABLE "parent" (
"id" INTEGER PRIMARY KEY,
"name" TEXT,
"email" TEXT,
"child_id" INTEGER
);
CREATE TABLE "child" (
"id" INTEGER PRIMARY KEY,
"name" TEXT
);
INSERT INTO parent
(id, name, email, child_id )
VALUES
(1, "Jim", "pineapple#fruit.com", 1 ),
(2, "Jane", "gizmo#gadget.com", 1 ),
(3, "Grover", "monty#python.com", 2 );
INSERT INTO child
(id, name)
VALUES
(1, "Ben" ),
(2, "Samantha" ),
(3, "Carl" );
My select query then gave me:
However, this data structure limits you to only on child per parent though I showed 2 parents for one of the kids. If you want multiple of either without having to duplicate the parent entries, you'd want to have a third table for the parent child relationship. That Table would have a parent_id, a child_id, and there are different schools of thought on whether it having it's own id would be required (it makes selecting specific rows in the relationship table easy and becomes more important if the relationship gains additional fields itself). Your query would need to join all the tables to the relationship table and if you did this, that part might look something like this:
from relationship r
join parent p
on p.relation_id = r.parent_id
join child c
on c.relation_id = r.child_id