select the last study (max) course according the user - php

Question

What I am doing?
I am displaying the user according to there studied.
I want to fetch the last course studied by each user.
Problem?
I am not getting the last course name according to last studied course. I am getting the first course name.(java) but i want (oracle) as last studied course by user.
User Table
user_id | Name
====================
1 | Zishan
2 | Ellen
Course Table
course_id | course_name | user_id | course_year
==================================================
1 | java | 1 | 2015
2 | C++ | 1 | 2017
3 | oracle | 1 | 2016
4 | dot net | 2 | 2016
Result Table
Name | last_course_name | last_course_year
============================================
Zishan | java | 2017
Ellen | dot net | 2016
Expected Result
Name | last_course_name | last_course_year
============================================
Zishan | C++ | 2017
Ellen | dot net | 2016
Query
SELECT `u`.`name`, MAX(`c`.`course_year`) as last_course_year , `c`.`course_name` as last_course_name
FROM `user` as `u`
LEFT OUTER JOIN `course` as `c` ON `u`.`id` = `c`.`user_id`
GROUP BY `u`.`id`
Active Record Query:
$this->db->select('u.name','c.course_name as last_course_name');
$this->db->select_max('c.course_year as last_course_year');
$this->db->from('user as u');
$this->db->join('course as c', 'u.id = c.user_id', 'left');
$this->db->join('course as c1', 'c.user_id = c1.user_id', 'left outer');
$this->db->where('c1.user_id IS NULL', null, false);
$this->db->group_by('u.id');
$user_couse_data_query = $this->db->get();

Answer 1

Here you go to the latest row from course table for each student
SELECT `u`.`name`, `c`.`course_name` as last_course_name ,c.course_year
FROM `user` as `u`
LEFT JOIN `course` as `c` ON `u`.`id` = `c`.`user_id`
LEFT JOIN `course` as `c1` ON `c`.`user_id` = `c1`.`user_id` AND `c`.`course_year` < `c1`.`course_year`
WHERE `c1`.`user_id` is null
Demo
Note it may return multiple courses if they share same year
Equivalent active record query will be something like
$this->db->select('u.name','c.course_name as last_course_name','c.course_year as last_course_year');
$this->db->from('user as u');
$this->db->join('course as c', 'u.id = c.user_id', 'left');
$this->db->join('course as c1', 'c.user_id = c1.user_id AND c.course_year < c1.course_year', 'left');
$this->db->where('c1.user_id IS NULL', null, false);
$user_couse_data_query = $this->db->get();

Answer 2

Try like this;
select U.Name, C.course_name as last_course_name, C2.maxCourseYear as last_course_year from User U
inner join
( select user_id,max(course_year) as maxCourseYear from Course C
group by C.user_id) C
ON U.user_id = C.user_id
inner join Course C2 ON C2.course_year = C.maxCourseYear

Answer 3

Your query does not work because you need to give all the columns in group by on which aggregate function is not applied.
Try this out:
select c.name,b.last_course_name,a.last_course_year
from
(select user_id,max(course_year) as last_course_year
from course_table
group by user_id) a
left join
course_table b
on a.user_id = b.user_id and a.course_year = b.course_year
left join
user_table c
on a.user_id = c.user_id;
Let me know in case of any queries.

Answer 4

Use the following subquery
SELECT u.name,
c.course_year as last_course_year,
c.course_name as last_course_name
FROM user as u
LEFT OUTER JOIN course as c ON u.id = c.user_id and
(c.user_id, c.course_year) IN
(
SELECT c.user_id, MAX(c.course_year)
FROM course as c
GROUP BY c.user_id
)