Getting sum from a left table of leftjoined table - mysql

Question

Below are the tables and the SQL query. I am doing a left join and trying to get SUM of a column that's in the left table and count from the right table.
Is it possible to get both in 1 query?
https://www.db-fiddle.com/f/3QuxG1DLgWJ8aGXNbnnwU1/1
select
s.test,
count(distinct s.name),
sum(s.score) score, -- need accurate score
count(a.id) attempts -- need accurate attempt count
from question s
left join attempts a on s.id = a.score_id
group by s.test
create table question (
id int auto_increment primary key,
test varchar(25),
name varchar(25),
score int
);
create table attempts (
id int auto_increment primary key,
score_id int,
attempt_no int
);
insert into question (test, name, score) values
('test1','name1', 10),
('test1','name2', 15),
('test1','name3', 20),
('test1','name4', 25),
('test2','name1', 15),
('test2','name2', 25),
('test2','name3', 30),
('test2','name4', 20);
insert into attempts (score_id, attempt_no) values
(1, 1),
(1, 2),
(1, 3),
(1, 4),
(2, 1),
(2, 2),
(2, 3),
(2, 4);

Answer 1

You need to pre-aggregate before the join:
select q.test, count(distinct q.name),
sum(q.score) score, -- need accurate score
sum(a.num_attempts) attempts -- need accurate attempt count
from question q left join
(select a.score_id, count(*) as num_attempts
from attempts a
group by a.score_id
) a
on q.id = a.score_id
group by q.test;
Here is a db-fiddle.

Answer 2

As Gordon said above, you can pre-aggregate, but his answer will get you the incorrect number of attempts, unfortunately. This is due to an issue with how you're structuring your DB schema. It looks like your question table really records scores of attempts at questions, and your attempts table is unnecessary. You should really have a question table that simply contains an ID and a name for the question, and a attempts table that contains an attempt ID, question ID, name, and score.
create table question (
id int auto_increment primary key,
test varchar(25)
);
create table attempts (
id int auto_increment primary key,
question_id int,
name varchar(25),
score int
);
Then your query becomes as simple as:
select
q.id as question_id,
count(distinct a.name) as attempters,
sum(a.score) as total_score,
count(a.id) as total_attempts
from question q join attempts a on q.id = a.question_id
group by q.id