SELECT all EXCEPT results in a subquery - mysql

Question

I have a query that joins several tables (3 or 4) and gets me results as expected.
SELECT DISTINCT test_title, stt_id FROM student_tests
LEFT JOIN student_test_answers ON sta_stt_num = stt_id
JOIN tests ON stt_test_id = test_id
WHERE student_test_answer_id IS NULL
I have another query that shows another set of data, it basically is this:
SELECT test_id, COUNT(*) AS theCount FROM tests
JOIN test_questions ON test_id= tq_test_id
WHERE type= 'THE_TYPE'
GROUP BY test_id
HAVING theCount = 1
So basically I want to NOT include the results of this second query in the first one. the test_id would be the joining fields.
I have tried a WHERE NOT EXISTS ( -the above query -) but that returns no results which is not correct. I also tried 'NOT IN ( )'
Is there a better way of doing this?

Answer 1

Try something like this:
(SELECT test_id, COUNT(*) AS theCount FROM tests
JOIN test_questions ON test_id= tq_test_id
WHERE type= 'THE_TYPE'
GROUP BY test_id
HAVING theCount = 1) outer
LEFT JOIN (
[OtherQuery]
) a ON outer.test_id = a.test_id
WHERE a.test_id IS NULL

Answer 2

Here is my answer. Left outer Join gives you the participant (test). If there are no matches in test_questions then it'll still return the test rows, but null for test_questions. So if you then look for any test_question.test_id that is null, you will get what you are looking for.
I would also be specific in your count clause and not do a count(*) just to ensure that mysql knows what you truly want to count.
create database test;
use test;
create table test
(
test_id int,
`the_type` varchar(20)
);
create table test_questions
(
test_question_id int,
test_id int,
`the_type` varchar(20)
);
insert into test values (1, 'history');
insert into test values (2, 'chemistry');
insert into test values (3, 'reading');
insert into test_questions values (1, 1, 'hard question');
insert into test_questions values (2, 1, 'medium question');
insert into test_questions values (3, 2, 'hard question');
insert into test_questions values (4, 2, 'easy question');
select * from test;
select * from test_questions;
select t.test_id, count(distinct t.test_id)
from test t
left outer join test_questions tq on tq.test_id = t.test_id
where
tq.test_id is null
group by
t.test_id

Answer 3

As written in the comment you should be able to do it like this:
SELECT
DISTINCT test_title,
olc_stt_i_num
FROM
student_tests
LEFT JOIN
student_test_answers
ON olc_sta_i_stt_num = olc_stt_i_num
INNER JOIN
ol_class_tests
ON stt_test_num = test_num
WHERE
student_test_answer_id IS NULL
-- added this: replace test_id with real column
AND ***test_id*** NOT IN (
SELECT
test_id
FROM
tests
JOIN
test_questions
ON test_id= tq_test_id
WHERE
type= 'THE_TYPE'
GROUP BY
test_id
HAVING
COUNT(*) = 1
)

Answer 4

What exactly is the second query? I only see one query here, and no sub-query. Also, a sqlfiddle of your precise schema would be helpful.
Anyhow, I think you want some sort of left excluding join. It looks something like this:
select test.test_id, count(*) as theCount
from tests test
join test_questions tq
on tq.test_id = test.test_id
left join tests excluded_test
on excluded_test.test_id = test.test_id
where tq.type = 'THE_TYPE'
and << Some condition that explains what excluded_test is >>
and excluded_test.test_id is null
EDIT: Yeah, there's definitely a lot of details missing from the original question (which had in some ways been mended), and which are still missing. Knowing the full table-structure of your example is important here, so it is difficult to provide a good concrete answer.