Ho to get last item in mysql using max() - mysql

Question

I want to get the last item as result using max(), but i'm just getting the first item even if im using max()
Here's the SQL code:
SELECT r.correct, r.items, r.percentage,MAX(r.date_taken) as date_taken,
u.username,u.FN, u.user_course_type,
IFNULL(u.user_major_type,'N/A') as user_major_type,u.level_name,
u.section_name
FROM bcc_fs_exam_result r
INNER JOIN
(SELECT u.id_user, u.username, CONCAT(u.lastname,', ',u.firstname) as FN,
c.user_course_type, m.user_major_type, l.level_name, s.section_name
FROM bcc_fs_user u
LEFT JOIN bcc_fs_user_course c on c.id_user_course = u.id_user_course
LEFT JOIN bcc_fs_user_major m on m.id_user_major = u.id_user_major
LEFT JOIN bcc_fs_group_level l ON l.id_level = u.id_level
LEFT JOIN bcc_fs_group_section s ON s.id_section = u.id_section
) u ON r.id_user = u.id_user WHERE r.id_exam = 5 GROUP BY r.id_user
TIA

Answer 1

What I take from your question is that you want to get the "correct", "items", "percentage" ect. columns of the row in bcc_fs_exam_result which has the last or first date.
If that's correct then you can filter bcc_fs_exam_result by first finding what is the min or max date by for each id_user then join that back on the exam results table.
SELECT
r.correct,
r.items,
r.percentage,
r.date_taken,
u.username,
u.FN,
u.user_course_type,
IFNULL(u.user_major_type,'N/A') as user_major_type,
u.level_name,
u.section_name
FROM bcc_fs_exam_result r
INNER JOIN (
SELECT u.id_user,
u.username,
CONCAT(u.lastname,', ',u.firstname) as FN,
c.user_course_type,
m.user_major_type,
l.level_name,
s.section_name
FROM bcc_fs_user u
LEFT JOIN bcc_fs_user_course c on c.id_user_course = u.id_user_course
LEFT JOIN bcc_fs_user_major m on m.id_user_major = u.id_user_major
LEFT JOIN bcc_fs_group_level l ON l.id_level = u.id_level
LEFT JOIN bcc_fs_group_section s ON s.id_section = u.id_section
) u ON r.id_user = u.id_user
INNER JOIN (
SELECT
id_user, max(r.date_taken) as last_date_taken
FROM bcc_fs_exam_result
GROUP BY id_user
) as lastdate ON lastDate.id_user = r.id_user and r.date_taken = lastdate.last_date_taken
which could be more simply written as :
SELECT
r.correct,
r.items,
r.percentage,
r.date_taken,
u.username,
CONCAT(u.lastname,', ',u.firstname) as FN,
c.user_course_type,
IFNULL(m.user_major_type,'N/A') as user_major_type,
l.level_name,
s.section_name
FROM bcc_fs_exam_result r
INNER JOIN (
SELECT
id_user, max(r.date_taken) as last_date_taken
FROM bcc_fs_exam_result
GROUP BY id_user
) as lastdate ON lastDate.id_user = r.id_user and r.date_taken = lastdate.last_date_taken
INNER JOIN bcc_fs_user u on r.id_user = u.id_user
LEFT JOIN bcc_fs_user_course c on c.id_user_course = u.id_user_course
LEFT JOIN bcc_fs_user_major m on m.id_user_major = u.id_user_major
LEFT JOIN bcc_fs_group_level l ON l.id_level = u.id_level
LEFT JOIN bcc_fs_group_section s ON s.id_section = u.id_section
You have assumed that id_user + date_taken is a surrogate key of bcc_fs_exam_result which you should probably enforce with a constraint if at all possible. Otherwise it looks from your sample data that the order of the unique id column id_result follows the date_takenso you might be better to use Max(id_result) rather than Max(date_taken). That would avoid returning duplicate rows for one id_user where two rows of bcc_fs_exam_result have the same taken_date and `id_user.