Deleting rows from multiple tables in MySQL

Delete a project from the projects table and all the images associated with that project in the images table.

Lets say $del_id = 10

The answer

<?php
  $query = sprintf("
  DELETE FROM p, i
  USING projects p, images i
  WHERE p.p_id = %d
    AND p.p_id = i.p_id
  ", $del_id);
?>

The test

projects

create table projects (
  p_id int unsigned not null auto_increment primary key
);
insert into projects (p_id) values (1),(2),(3);
select * from projects;
-- +------+
-- | p_id |
-- +------+
-- |    1 | 
-- |    2 | 
-- |    3 | 
-- +------+

images

create table images (
  i_id int unsigned not null auto_increment primary key,
  p_id int unsigned default null
);
insert into images (p_id) values (1),(1),(1),(2),(2),(3),(3);
select * from images;
-- +------+------+
-- | i_id | p_id |
-- +------+------+
-- |    1 |    1 | 
-- |    2 |    1 | 
-- |    3 |    1 | 
-- |    4 |    2 | 
-- |    5 |    2 | 
-- |    6 |    3 | 
-- |    7 |    3 | 
-- +------+------+

the delete

delete from p, i
using projects p, images i
where p.p_id = i.p_id
 and  p.p_id = 1;

the result

select * from projects;
-- +------+
-- | p_id |
-- +------+
-- |    2 | 
-- |    3 | 
-- +------+

select * from images;
-- +------+------+
-- | i_id | p_id |
-- +------+------+
-- |    4 |    2 | 
-- |    5 |    2 | 
-- |    6 |    3 | 
-- |    7 |    3 | 
-- +------+------+