I feel like this should be really easy to do an I am just making some small mistake somewhere. Probably should add that I am a teacher and not a coder, so I'm not well versed in SQL. In addition, I did look at a bunch of questions here and none of them quite worked.
I have the table student_answers(id, student_id, question_id, answer, result, date_time)
I want to get the question_id
, answer
, result
and date_time
for the last answer a student entered for each question. So if they answered three times for question 7, I only want to see the last answer
and result
that they entered.
For teaching purposes I can not simply update each row as they re-enter answers.
I tried the following queries
SELECT id, question_id, answer, result, date FROM Student_Answers
WHERE student_id = 505 AND question_id in (select id from Test_Questions q where q.test_id = 37)
Group by question_id
having date = max(date)
ORDER BY Student_Answers`.`question_id` ASC
but that didn't include the questions with multiple answers at all, and only have me the questions that student 505 answered once. Student 505 answered questions 3 and 4 twice and the rest only once, and I only saw results for 1, 2 and 5.
I tried this query
SELECT
b.*
FROM
(
SELECT question_id, MAX(date) AS maxdate
FROM TP_Student_Answers
GROUP BY question_id
) a
INNER JOIN
TP_Student_Answers b ON
a.question_id = b.question_id AND
a.maxdate = b.date
and b.student_id = 505
and b.question_id in (select id from TP_Questions q where q.test_id = 37)
ORDER BY
b.question_id
but this on only gave me 3 and 4 and none of the ones he attempted only once. Any help would be greatly appreciated!
This is a sample of the data:
id student_id question_id answer result date
7133 505 1 a correct 2012-11-16 09:03:58
7134 505 2 c wrong 2012-11-16 09:03:58
7135 505 3 e wrong 2012-11-16 09:03:58
7136 505 3 d wrong 2013-12-16 09:03:58
7137 505 4 c correct 2012-11-16 09:03:58
7138 505 4 d wrong 2013-12-16 09:03:58
7139 505 5 blank 2012-11-16 09:03:58
when I run the query I would like to see:
7133 505 1 a correct 2012-11-16 09:03:58
7134 505 2 c wrong 2012-11-16 09:03:58
7136 505 3 d wrong 2013-12-16 09:03:58
7138 505 4 d wrong 2013-12-16 09:03:58
7139 505 5 blank 2012-11-16 09:03:58
Notice entries 7135 and 7137 are omitted since there is a later answer for each of those questions
Check this query: (gives all the students with latest answers to all questions)
SELECT id, student_id, question_id, answer, result, date_time
FROM (SELECT *,
CASE
WHEN (@prevQ = question_id AND @prevS = student_id)
THEN
@marker := 0
ELSE
@marker := 1
END
AS marker,
@prevS := student_id,
@prevQ := question_id
FROM student_answers
ORDER BY student_id ASC, question_id ASC, date_time DESC) aView,
(SELECT @prevQ = -1, @prevS = -1) a
WHERE marker = 1;
and for a specific student_id
and specific question_id
s:
SELECT id, student_id, question_id, answer, result, date_time
FROM (SELECT *,
CASE
WHEN (@prevQ = question_id AND @prevS = student_id)
THEN
@marker := 0
ELSE
@marker := 1
END
AS marker,
@prevS := student_id,
@prevQ := question_id
FROM student_answers
WHERE student_id = 501
AND question_id IN (SELECT id
FROM TP_Questions q
WHERE q.test_id = 37)
ORDER BY student_id ASC, question_id ASC, date_time DESC) aView,
(SELECT @prevQ = -1, @prevS = -1) a
WHERE marker = 1;
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