在CodeIgniter中选择唯一值

Question

我正在尝试从最近的搜索表中仅检索唯一值。

public function get5RecentSearch()
{  
    $this->db->select('recent_search.*, category.category_name, category_two.cat_name,');
    $this->db->from('recent_search');
    $this->db->order_by("date", "desc");
    $this->db->join('category', 'category.category_id = recent_search.category_one', 'left');
    $this->db->join('category_two', 'category_two.cat_id = recent_search.category_two', 'left');
    $this->db->limit(5);
    $query = $this->db->get()->result_array();
    return $query;
}

我已经尝试使用$this->db->distinct();，但是没有用。我想念什么？

public function get5RecentSearch()
{  
    $this->db->select('recent_search.*, category.category_name, category_two.cat_name,');
    $this->db->from('recent_search');
    $this->db->order_by("date", "desc");
    $this->db->join('category', 'category.category_id = recent_search.category_one', 'left');
    $this->db->join('category_two', 'category_two.cat_id = recent_search.category_two', 'left');
    $this->db->limit(5);
    $this->db->distinct();
    $query = $this->db->get()->result_array();
    return $query;
}