(8)SELECT (9)DISTINCT (11)<TOP_specification> <select_list>
(1)FROM
(3) <join_type> JOIN <right_table>
(2) ON
(4)WHERE
(5)GROUP BY <group_by_list>
(6)WITH {CUBE | ROLLUP}
(7)HAVING
(10)ORDER BY <order_by_list>
(11)LIMIT
查询处理的每一个阶段 FORM: 对FROM的左边的表和右边的表计算笛卡尔积。产生虚表VT1 ON: 对虚表VT1进行ON筛选,只有那些符合