Grouping by Count(*) following multiple join operations - mysql

Question

Trying to figure out what I thought was a simple query-
I have the following tables with schemas as follows.
models(id: int, first_name: string, last_name: string)
painters(id: int, first_name: string, last_name:string)
portraits_painters(painter_id: int, portrait_id: int)
roles(model_id: int, portrait_id: int)
I am trying to satisfy this query: The first name, last name, and count
for painters who have been the model for their own painting- i.e. where the count column for a first and last name is the number of self portraits the painter has done (both the painter and model). (Safe to assume equal first names and last names mean the same individual).
If a painter has no self portraits they should not even be included in the final output.
SELECT
models.first_name,
models.last_name,
COUNT(portraits_painters.portrait_id)
FROM models
RIGHT JOIN painters
ON models.first_name = painters.first_name
AND models.last_name = painters.last_name
RIGHT JOIN portraits_painters
ON portraits_painters.painter_id = painters.id
RIGHT JOIN roles
ON roles.portrait_id = portraits_painters.portrait_id
GROUP BY portraits_painters.portrait_id;
I essentially tried to narrow the table down to rows where names matched, followed by instances where the painter ids matched and the portrait id's matched, but evidently there's something incorrect in how I am joining tables.
I'm also getting errors in regards to the GROUP BY portion, so not sure if there's a better way to approach it? Perhaps aliasing?

Answer 1

You can get the names of the models and painters using:
select m.first_name, m.last_name, p.first_name, p.last_name
from roles r join
portraits_painters pp
on pp.portrait_id = r.portrait_id join
painters p
on p.id = pp.painter_id join
models m
on m.id = r.model_id;
The rest is just a where and group by:
select p.first_name, p.last_name, count(*)
from roles r join
portraits_painters pp
on pp.portrait_id = r.portrait_id join
painters p
on p.id = pp.painter_id join
models m
on m.id = r.model_id
where m.first_name = p.first_name and m.last_name = p.last_name
group by p.first_name, p.last_name;
I am not sure what thinking leads to outer joins or exists clauses.

Answer 2

Get painter infos for all portraits:
SELECT p.first_name, p.last_name, pp.portrait_id
FROM portraits_painters AS pp
JOIN painters AS p
ON pp.painter_id = p.id
Get model infos for all portraits:
SELECT m.first_name, m.last_name, pp.portrait_id
FROM roles AS r
JOIN models AS m ON m.id = r.model_id
JOIN portraits_painters AS pp ON pp.portrait_id = r.portrait_id
Combine these two tables on the same first_name and last_name. Now you get both painter infos and model infos for every portrait. Just group the records by first_name and last_name, and COUNT for each group, you get what you want.
So, the final query would be:
SELECT a.first_name, a.last_name, COUNT(a.portrait_id)
FROM
(
SELECT p.first_name, p.last_name, pp.portrait_id
FROM portraits_painters AS pp
JOIN painters AS p
ON pp.painter_id = p.id
) AS a
JOIN
(
SELECT m.first_name, m.last_name, pp.portrait_id
FROM roles AS r
JOIN models AS m ON m.id = r.model_id
JOIN portraits_painters AS pp ON pp.portrait_id = r.portrait_id
) AS b
ON a.first_name = b.first_name AND a.last_name = b.last_name
GROUP BY a.first_name, a.last_name;