Need T-SQL query to get multiple choice answer if matches - sql

Question

Example:
Table Question_Answers:
+------+--------+
| q_id | ans_id |
+------+--------+
| 1 | 2 |
| 1 | 4 |
| 2 | 1 |
| 3 | 1 |
| 3 | 2 |
| 3 | 3 |
+------+--------+
User_Submited_Answers:
| q_id | sub_ans_id |
+------+------------+
| 1 | 2 |
| 1 | 4 |
| 2 | 1 |
| 3 | 1 |
| 3 | 2 |
| 3 | 4 |
+------+------------+
I need a T-SQL query if this rows matches count 1 else 0

Answer 1

SELECT
t1.q_id,
CASE WHEN COUNT(t2.sub_ans_id) = COUNT(*)
THEN 1
ELSE 0 END AS is_correct
FROM Question_Answers t1
LEFT JOIN User_Submited_Answers t2
ON t1.q_id = t2.q_id AND
t1.ans_id = t2.sub_ans_id
GROUP BY t1.q_id

Answer 2

Try the following code:
select qa.q_id,case when qa.ans_id=sqa.ans_id then 1 else 0 end as result from questionans qa
left join subquestionans sqa
on qa.q_id=sqa.q_id and qa.ans_id=sqa.ans_id

Answer 3

This should give you expected result for every question.
select q_id, min(Is_Correct)Is_Correct from (
select Q.q_id,case when count(A.sub_ans_id)=count(*) then 1 else 0 end as Is_Correct
from #Q Q left join #A A on Q.q_id=A.q_id and Q.ans_id=A.sub_ans_id
group by Q.q_id
UNION ALL
select A.q_id,case when count(Q.ans_id)=count(*) then 1 else 0 end as Is_Correct
from #Q Q right join #A A on Q.q_id=A.q_id and Q.ans_id=A.sub_ans_id
group by A.q_id ) I group by q_id

Answer 4

MySQL solution (sql fiddle):
SELECT tmp.q_id, MIN(c) as correct
FROM (
SELECT qa.q_id, IF(qa.q_id = usa.q_id, 1, 0) as c
FROM question_answers qa
LEFT JOIN user_submited_answers usa
ON qa.q_id = usa.q_id AND qa.ans_id = usa.sub_ans_id
UNION
SELECT usa.q_id, IF(qa.q_id = usa.q_id, 1, 0) as c
FROM question_answers qa
RIGHT JOIN user_submited_answers usa
ON qa.q_id = usa.q_id AND qa.ans_id = usa.sub_ans_id
) tmp
GROUP BY tmp.q_id;
Now, step by step explanation:
In order to get the right output we will need to:
extract from question_answers table the answers which were not filled in by the user (in your example: q_id = 3 with ans_id = 3)
extract from user_submited_answers table the wrong answers which were filled in by the user (in your example: q_id = 3 with sub_ans_id = 4)
To do that we can use a full outer join (for mysql left join + right join):
SELECT *
FROM question_answers qa
LEFT JOIN user_submited_answers usa
ON qa.q_id = usa.q_id AND qa.ans_id = usa.sub_ans_id
UNION
SELECT *
FROM question_answers qa
RIGHT JOIN user_submited_answers usa
ON qa.q_id = usa.q_id AND qa.ans_id = usa.sub_ans_id;
From the previous query results, the rows which we are looking for (wrong answers) contains NULL values (based on the case, in question_answers table or user_submited_answers table).
The next step is to mark those rows with 0 (wrong answer) using an IF or CASE statement: IF(qa.q_id = usa.q_id, 1, 0).
To get the final output we need to group by q_id and look for 0 values in the grouped rows. If there is at least one 0, the answer for that question is wrong and it should be marked as that.
Check sql fiddle: SQL Fiddle