Question

I have three tables: projects, lists, items.

The project joins to the lists on project_id, and the items join to the lists on list_id, and the goal is to have all of the row data for each.

What have I tried?
Well, I actually have only been able to do it by having three separate queries / outputs and then just iterating through them with PHP to combine data.

Is it possible to write the query so that way I end up with one data object that I can easily iterate through?

project (w details)
-- list (and its details)
----- item (w details)
----- item (w details)
----- item (w details)
-- list (w details)
----- item (w details)
----- item (w details)

Answer 1

You mean like this:

select
    a.project_id,
    b.list_id,
    c.item_id
from
    projects a
        join lists b
            on a.project_id=b.project_id
        join items c
            on b.list_id=c.list_id

Output will be something like:

project_id | list_id | item_id
 1         | 5       |  45
 1         | 5       |  46
 1         | 8       |  12

Or did you want to return all the parts of it in a single row?

If you want a single row, you can do something along the lines of:

select
    a.project_id,
    group_concat(b.list_id) as listIDs,
    group_concat(c.item_id) as itemIDs
from
    projects a
        join lists b
            on a.project_id=b.project_id
        join items c
            on b.list_id=c.list_id

But it will get messier in PHP to deal with all the grouped stuff.

Output will be something like:

project_id | list_id | item_id
 1         | 5,8     |  45, 46, 12

You could also mix and match the two to maybe get the best of both worlds:

select
    a.project_id,
    b.list_id as listIDs,
    group_concat(c.item_id) as itemIDs
from
    projects a
        join lists b
            on a.project_id=b.project_id
        join items c
            on b.list_id=c.list_id

Output will be something like:

project_id | list_id | item_id
 1         | 5       |  45, 46
 1         | 8       |  12