0.SQL标准的执行流程（select）

(8)  SELECT
(9)  DISTINCT
(11) <TOP_specification> <select_list>
(1)  FROM <left_table>
(3)  <join_type> JOIN <right_table>
(2)  ON <join_condition>
(4)  WHERE <where_condition>
(5)  GROUP BY <group_by_list>
(6)  WITH {CUBE ROLLUP}