$this->db->select();  //選擇查詢的字段$this->db->select_max();$this->db->select_min();$this->db->select_avg();$this->db->select_sum();$this->db->from();   //選擇表名$this->db->join();$this->db->get();   //得到查詢結果$this->db->get_where();$this->db->where();$this->db->or_where();$this->db->where_in();$this->db->or_where_in();$this->db->where_not_in();$this->db->or_where_not_in();$this->db->like();$this->db->or_like();$this->db->not_like();$this->db->or_not_like();$this->db->group_by();$this->db->distinct();$this->db->having();$this->db->or_having();$this->db->order_by();$this->db->limit();$this->db->count_all_results();

$this->db->insert();

$this->db->set();$this->db->update();

$this->db->delete();

$this->db->empty_table();$this->db->truncate();

$this->db->start_cache()$this->db->stop_cache()$this->db->flush_cache()

result()  //返回對象數組result_array() //返回二維數組row()   //返回一個對象row_array()  //返回一維數組num_rows()  //返回查詢的行數num_fields() //返回查詢結果的字段數free_result() //釋放查詢所占的資源內存

$this->db->insert_id()  //獲取剛剛插入的id$this->db->affected_rows() //修改或插入影響的行數$this->db->count_all();  //統計記錄的總條數 這一函數加入where條件無效$this->db->last_query();  //最后一條執行的sql語句//注意以下兩個函數僅返回sql語句 不執行sql語句$data = array('name' => $name, 'email' => $email, 'url' => $url);$str = $this->db->insert_string('table_name', $data);$data = array('name' => $name, 'email' => $email, 'url' => $url);$where = "author_id = 1 AND status = 'active'";$str = $this->db->update_string('table_name', $data, $where); //返回正確格式的更新字符串