fetching value from database - mysql

Question

This is the data am having in my table named rent
id date stud_id paid balance
18 10-2016 94 15000 15000
19 10-2016 94 10000 5000
20 10-2016 96 25000 5000
21 10-2016 96 5000 0
here i want to get last inserted stud_id balance but am getting the first one.
my code looks like this
public function rent_outstanding($hos,$dt)
{
$this->db->select('student_hostel.*,rent.balance,rent.paid');
$this->db->join('rent','rent.stud_id=student_hostel.id');
$this->db->where('status!=','G');
$this->db->where('status!=','R');
$this->db->where('hostel',$hos);
$this->db->where('rent.date',$dt);
$this->db->select_sum('paid');
$this->db->group_by('stud_id');
$query=$this->db->get('student_hostel');
return $query;
}
my student_hostel table looks like this
id first_name last_name stud_id admit_date hostel class room bed status
94 ss ff PHBH00094 01-10-2016 12 16 115 501A P
96 maltu uv PHBH00096 01-10-2016 12 16 115 501C p
am getting my result like this
SI.No STUDENT ID NAME RENT PAID BALANCE
1 PHBH00094 Ss 30000 25000 15000
2 PHBH00096 Maltu 30000 30000 5000
i want to get my result like this
SI.No STUDENT ID NAME RENT PAID BALANCE
1 PHBH00094 Ss 30000 25000 5000
2 PHBH00096 Maltu 30000 30000 0

Answer 1

You need to specify somewhere to take the max of ID from rent table.
This query should give you that.
select stud_id ,first_name, paid, balance from rent rt, student_hostel s where
hostel='$hosr' and ent.date='$dt' and id = (select max(id) from rent r where r.stud_id = rt.stud_id) and status!= 'G' and status!= 'R'
Add date to inner query if you need balance of that date id = (select max(id) from rent r where r.stud_id = rt.stud_id and r.date='$dt')
For Codeignitor you can write the query directly:
$sql = "select stud_id ,first_name, paid, balance from rent rt, student_hostel s where hostel=? and ent.date=? and id = (select max(id) from rent r where r.stud_id = rt.stud_id) and status!= 'G' and status!= 'R'";
$this->db->query($sql, array($hosr, $dt));
More info here: https://www.codeigniter.com/userguide3/database/queries.html#query-bindings