MYSQL Join Statement - im lost - php

Question

OK, I need to get some data from multiple tables, all of which have a key.
Projects (key:id)
Projects_users (key:project_id,user_id)
Users (key:id)
Basically each project can have N users on it. I need to get all the users that are in each project in a formatted response.
For instance:
projects = {[
1: {
'title':'Project 1',
'users': [
1: { id: 23, name:'john' },
2: { id: 55, name:'sally' }
]
}
2: {
'title':'Project 2',
'users': [
1: { id: 41, name:'jeff' },
2: { id: 55, name:'sally' }
]
}
]}
Also, I understand I can do this in PHP with multiple MYSQL statements. Would that be faster and do the concatenation in PHP, or letting MYSQL do this be more efficient / quick.

Answer 1

You can use following statement to get the desired data:
SELECT `Projects`.*, `Users`.* FROM
`Projects` JOIN (
`Projects_users` JOIN
`Users`
ON `Projects_users`.`user_id` = `Users`.`id`
)
ON `Projects`.`id` = `Projects_users`.`project_id`
ORDER BY `Projects`.`id`
After that, you can traverse the resulting table in single pass and build the array you want.

Answer 2

I haven't tried this, but it should be close to what you're looking for:
select p.title, u.name
from projects p inner join users u
on p.id = u.id
order by p.title
You need the "join" to get the data .. but use PHP to format it.
PS:
"projects" is one table, "users" is a second table ... and the "projects" table needs to hold "foreign keys" for user IDs 23, 55 and 41.

Answer 3

MySql won't be able to return data in a tree-like structure like you want. You can do this in two ways:
Get all projects in one data set and all users associated to those projects on a second data set. You would have to write the code that generates the JSON objects you need.
Just get one data set doing an inner join of the project's table with the user's table. You will get repeated information on many columns but you will get everything in one sql statement. You could then iterate through the result set and generate the structure you need.
If you need help with the inner join, it would be something like:
select p.title, u.id, u.name
from projects p
inner join project_users pu on pu.project_id=p.id
inner join users u on u.id=pu.user_id