How to get fields from multiple tables - sql

Question

I want to get fields from 2 different tables . The last field candidate_score_id has a many to one relationship. So how should I join the below 2 queries
1) To get candidate_score_id from the candidate_score table.
select candidate_score_id from candidate_score a where
a.assessment_id = NEW.assessment_id and
a.candidate_id = NEW.candidate_id and
a.attempt_Count = NEW.attempt_count;
2) To insert different fields in to the candidate_score_details table. The field in this table should be obtained by query above.
insert into candidate_score_details(candidate_score_details_id, candidate_id, assessment_id, attempt_count, score_type, score_tag,correct, candidate_score_id)
select uuid();
select a.candidate_id, a.assessment_id,a.attempt_count,"BY-COMPLEXITY",
case c.complexity
when 1 then "HIGH"
when 2 then "MEDIUM"
when 3 then "LOW"
end, count(*) from candidate_answer a, answer_key b, question_meta_data c where a.candidate_id = NEW.candidate_id and
a.assessment_id = NEW.assessment_id and
a.attempt_count = NEW.attempt_count and
a.assessment_id = b.assessment_id and
a.question_id = b.question_number and
a.response = b.answer and
a.question_id = c.question_number
group by a.candidate_id, a.assessment_id, a.attempt_count, c.complexity;

Answer 1

Just looking at the SQL joining aspect of your question, you'll need to specify the table I THINK you're aliasing a 2nd table with the "NEW" reference. If that's the case, then the query would be (replacing "OTHER_TABLE_NAME" with the name of the 2nd table:
select a.candidate_score_id
from candidate_score a
left join OTHER_TABLE_NAME new on
and a.assessment_id = NEW.assessment_id
and a.candidate_id = NEW.candidate_id
and a.attempt_Count = NEW.attempt_count

Answer 2

Seems that Query 1 has the same 3 criteria on the "candidate_score" table as for the "candidate_answer" table in Query 2.
So how about adding a LEFT JOIN of "candidate_score" to "candidate_answer" on those 3 fields?
For example:
INSERT INTO candidate_score_details
(
candidate_score_details_id,
candidate_id,
assessment_id,
attempt_count,
score_type,
score_tag,
correct,
candidate_score_id
)
SELECT
uuid(),
answer.candidate_id,
answer.assessment_id,
answer.attempt_count,
'BY-COMPLEXITY' AS score_type,
(CASE meta.complexity
WHEN 1 THEN 'HIGH'
WHEN 2 THEN 'MEDIUM'
WHEN 3 THEN 'LOW'
END) AS score_tag,
COUNT(*) AS correct,
MAX(score.candidate_score_id) AS max_candidate_score_id
FROM candidate_answer AS answer
JOIN answer_key AS akey
ON (akey.assessment_id = answer.assessment_id AND akey.question_number = answer.question_id AND akey.answer = answer.response)
LEFT JOIN candidate_score AS score
ON (score.candidate_id = answer.candidate_id AND score.assessment_id = answer.assessment_id AND score.attempt_count = answer.attempt_count)
LEFT JOIN question_meta_data AS meta
ON meta.question_number = answer.question_id
WHERE answer.candidate_id = NEW.candidate_id
AND answer.assessment_id = NEW.assessment_id
AND answer.attempt_count = NEW.attempt_count
GROUP BY answer.candidate_id, answer.assessment_id, answer.attempt_count, meta.complexity;