根据用户选择最后一个学习（最大）课程

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();

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();

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.

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

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
                )