Finding out how two tables are connected by looking in a third - sql

Question

I have a couple of tables:
boxes Table ToysTable Kitchen Table
boxId | ID Name | ID Type | ID
------------- -------------- -----------
1 | TOY1 Ball | TOY1 Fork | KIT1
1 | TOY2 Car | TOY2 Knife | KIT2
1 | KIT1 Puzzle | TOY3 Spoon | KIT3
2 | KIT2
I want to find what box contains my stuff.
So if I ask:
What box contains a fork and my car toy.
I want to get the Id of that box, in this case 1.
How would I do this ?
Sqlfiddle: http://sqlfiddle.com/#!4/11b0a/3/0
Edit:
Updated column name on kitchen to type.
Edit2:
Final solution became something like this (Thanks Gordon):
select b.boxid
from boxes b left join
(select id, 'toy' type
from toys t
where t.name in ('Car', 'Fork')
union all
select id, 'kitchen' type
from kitchen k
where k.name in ('Car', 'Fork')
) tk
on b.id = tk.id
group by b.boxid
having count(distinct tk.type) = 2;

Answer 1

This is a bit tricky, because the id could be to either table. One solution is group by with a union all. Here is a generic approach, assuming that the ids in the two reference table have different values:
select b.boxid
from boxes b left join
(select id, name
from toys t
union all
select id, name
from kitchen k
) tk
on b.id = tk.id
group by b.boxid
having sum(case when tk.name = 'Car' then 1 else 0 end) > 0 and
sum(case when tk.name = 'Fork' then 1 else 0 end) > 0;
Note: In MySQL, I would write this query as:
select b.boxid
from boxes b left join
(select id, name
from toys t
where t.name in ('Car', 'Fork')
union all
select id, name
from kitchen k
where k.name in ('Car', 'Fork')
) tk
on b.id = tk.id
group by b.boxid
having count(distinct name) = 2;
You could write it this way in any SQL dialect, actually.