如何在MySQL中比较MySQL中的DateTime日期和时间

Question

I have a column StartTime and EndTime in database and I'm trying to compare Date & Time from a submit in mySQL.

Here is what I've tried:

public function checksched(){

        $this->db->where('employee_id', $this->input->post('employee_id'));
        $this->db->where('StartTime <=', $this->input->post('StartDate').' '.$this->input->post('StartTime'));
        $this->db->where('EndTime >=', $this->input->post('EndDate').' '.$this->input->post('EndTime'));
        $query = $this->db->get('maintenance');
        if($query->num_rows() == 1){
            return false;
        } else {
            return true;
        }

    }