MySql subqueries and max or group by? -
i have table:
id student class question answer time 1 1 1 1 c 12:30 2 1 1 1 d 12:36 3 1 1 2 12:38 4 2 1 1 b 11:24 5 2 1 1 c 11:26 6 2 1 3 d 11:35 7 2 3 3 b 11:24
i'm trying write query this:
for each student in specific class select recent answer each question.
so, choosing class "1" return:
id student class question answer time 2 1 1 1 d 12:36 3 1 1 2 12:38 5 2 1 1 c 11:26 6 2 1 3 d 11:35
i've tried various combinations of subqueries, joins, , grouping, nothing working. ideas?
you can use sub-query recent answer
per question
, use derived table , join original table:
select m.* mytable m inner join ( select student, question, max(`time`) mtime mytable class = 1 group student, question ) d on m.student = d.student , m.question = d.question , m.`time` = d.mtime m.class = 1
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