Nested query in codeigniter - php

Question

there are somethings wrong at
$this->db->where("Mark_ID,(SELECT Mark_ID FROM mark WHERE Course_ID=$Course_ID && Matric_No=$Matric_No)");
in my model?any suggestion idea?thank you.
function update_record($Course_ID,$Matric_No)
{
if($Course_ID && $Matric_No != NULL)
{
$data = array(
//'Course_ID' => $this->input->post('Course_ID'),
'Matric_No' => $this->input->post('Matric_No'),
'Student_Name' => $this->input->post('Student_Name'),
'Result_Mark_1' => $this->input->post('Result_Mark_1'),
'Result_Mark_2' => $this->input->post('Result_Mark_2'),
'Result_Mark_3' => $this->input->post('Result_Mark_3'),
'Result_Mark_4' => $this->input->post('Result_Mark_4'),
'Result_Mark_5' => $this->input->post('Result_Mark_5')
);
$this->db->where("Mark_ID,(SELECT Mark_ID FROM mark WHERE Course_ID=$Course_ID && Matric_No=$Matric_No)");
$this->db->update('mark', $data);
}
}

Answer 1

You need to use IN() clause
$subquery="SELECT Mark_ID FROM mark WHERE Course_ID=$Course_ID && Matric_No=$Matric_No";
$this->db->where("Mark_ID IN($subquery)",null,FALSE);
But you are using subquery from same table to update you will face the error of
you can't specify target table in update query
For this you need to give new alias to your subquery like
$subquery="SELECT t.Mark_ID FROM(
SELECT Mark_ID
FROM mark
WHERE Course_ID=$Course_ID && Matric_No=$Matric_No
) t ";
$this->db->where("Mark_ID IN($subquery)",null,FALSE);

Answer 2

I think you can use below code for get your result.
$this->db->select("Mark_id");
$this->db->where("Course_ID",$Course_ID);
$get_id = $this->db->get($this->tbl_user)->row();
after getting mark id simply pass it to below query.
$this->db->where('Mark_id', $get_id->Mark_id);
$this->db->update($this->tbl_user,$data);

Answer 3

I suggest you to make your life easier by forgetting about nested queries. If you still want to use nested query, answer posted above is correct. You need to use IN
function update_record($Course_ID,$Matric_No)
{
if($Course_ID && $Matric_No != NULL)
{
$data = array(
//'Course_ID' => $this->input->post('Course_ID'),
'Matric_No' => $this->input->post('Matric_No'),
'Student_Name' => $this->input->post('Student_Name'),
'Result_Mark_1' => $this->input->post('Result_Mark_1'),
'Result_Mark_2' => $this->input->post('Result_Mark_2'),
'Result_Mark_3' => $this->input->post('Result_Mark_3'),
'Result_Mark_4' => $this->input->post('Result_Mark_4'),
'Result_Mark_5' => $this->input->post('Result_Mark_5')
);
// pre update query
$this->db->select('Mark_id');
$this->db->where('Course_ID', $Course_ID);
$this->db->where('Matric_No', $Matric_No);
$tmp_result = $this->db->get();
$result = $tmp_result->row();
$mark_id = $result->Mark_id;
//updation
$this->db->where("Mark_ID",$mark_id);
$this->db->update('mark', $data);
}
}