get greatest Id from multiple table and remove duplicate value - mysql

Question

i got some problem obtaining value from my db,this is my first db
ID_HARGA ID_USER ID_BAG_PEMASARAN ID_ITEM HARGA ENTRY_DATE
1 9 1 3 1000000 2015-01-11 09:55:27
2 9 1 5 2000000 2015-01-13 07:19:10
5 9 1 3 3000000 2015-01-13 13:47:32
6 9 1 43 7000000 2015-01-13 13:49:49
13 9 1 50 3000000 2015-01-13 17:56:54
37 9 1 50 100 2015-01-19 09:08:20
this is the second one
ID_ITEM NAMA_ITEM SPEC_ITEM MASA_GARANSI STATUS_ITEM DIR_IMAGE
3 water heater emas bagus sekali selamanya 1
5 water heater tembaga bagus super selamanya 1
43 water hater heater seupo 3 1 water_22.jpg
50 tankkk 50 Liter 1 1 water_2.jpg
i know there is some null value just igniore it, i already did this
public function get_item()
{
//menghitung jumlah varian barang yang ada
$querycounter = $this->db->query('select * from ITEM WHERE STATUS_ITEM = 1');
$counter = $querycounter->num_rows();
$this->db->select('ITEM.ID_ITEM,NAMA_ITEM,SPEC_ITEM,HARGA,DIR_IMAGE');
$this->db->from('ITEM');
$this->db->join('HARGA', 'ITEM.ID_ITEM = HARGA.ID_ITEM','left');
// $this->db->order_by('ENTRY_DATE','DESC');
//$this->db->limit($counter);
$this->db->where('STATUS_ITEM',1);
//$query = $this->db->query('select from ITEM i join HARGA h on i.ID_ITEM = h.ID_ITEM order by h.ENTRY_DATE ASC');
$query = $this->db->get();
return $query->result_array();
//$this->db->select('nama_item','spec_item');
//$query = $this->db->get('item');
}
what i want is,just ignore dir_image
ID_ITEM NAMA_ITEM HARGA DIR_IMAGE
3 water heater emas 1000000
5 water heater tembaga 3000000
43 water hater 7000000
50 tankk 100
ID_item with biggest number not the old , so everytime i am insert into id_harga with ID_ITEM
the result always the newest HARGA
Thx before

Answer 1

There is a little confession that, do you want to get the maximum hagra, or newest inserted data (identifiable by HAGRA_ID if its auto increment by 1) in Hagra table. Your Code should be like
$this->db->select('ITEM.ID_ITEM,NAMA_ITEM,SPEC_ITEM,max(HARGA),DIR_IMAGE');
$this->db->from('ITEM');
$this->db->join('HARGA', 'ITEM.ID_ITEM = HARGA.ID_ITEM','left');
$this->db->where('STATUS_ITEM',1);
$this->db->group_by('item.item_id');
This will join your tables and select maximum value of Hagra. To use Max function, you need to use group_by(CodeIgniter Documentation) clause, other wise it will show only the single maximum value. Group_by will help to show maximum value of each group (each item);
If you want to get the newest inserted data, you can use the same technique using
$this->db->select('MAX(HAGRA_ID),ITEM.ID_ITEM,NAMA_ITEM,SPEC_ITEM,HARGA,DIR_IMAGE');