Codeigniter在where子句中的未知列？

I am trying to create an update function in Codeigniter using a dropdown menu. Unfortunately, when I click submit I get an error that there is an "Unknown column 'stages.id' in my where clause. I've used the stages.id in other parts of my code to update other fields, and am not sure why this is happening here. Any assistance or thoughts on why this might be happening would be greatly appreciated!

function update_stage_name($id){

  $stage_name=array(
    'stage_name'=>$this->input->post('stage_name')
  );

  $this->db->where('stages.id', $id);
  $this->db->update('stage_names', $stage_name);

}

This is what the database query looks like according to the error:

UPDATE `stage_names` SET `stage_name` = 'Holly' WHERE `stages`.`id` = '264'

I have several tables, and stages is sort of the main one. Stages each only have one stage_name but a stage_name can belong to multiple stages. Stage_name does not have a foreign key from stages, but stages has a stage_name_id.

EDIT: So it seems the issue was actually that I wanted to update the stages table, and not the stage_names table. But the problem is that the stages table has a stage_name_id but the input from my form is for stage_name. How do I get to the id in the same method? I'm still new to active record and codeigniter and i'm not sure how to proceed.

Try this:

function update_stage_name($id) {
    $stage_name=array(
        'stage_name'=> $this->input->post('stage_name')
    );

    $this->db->where('stage_names.id', (int)$id);
    $this->db->update('stage_names', $stage_name);
}

As the error says you dont have a column that can be referenced using stages.id. Mainly because its the wrong table..

Try..

UPDATE `stage_names` SET `stage_name` = 'Holly' WHERE `stage_names`.`id` = '264'
//Note changed the table name in the where

If you need to use the stages.id and (as you say in your comment) you dont have an FK then you will need to create one as the database isnt smart enough to guess it. So once you have a field in stages_names called stage_id (or similar) you can do..

UPDATE `stage_names` SET `stage_name` = 'Holly' WHERE `stage_id` = '264'