1 内层表可以利用外层表。例子如下:
1 select t1.CITY_ID, 2 t1.CITY_NAME, 3 t1.PRO_ID, 4 (select t2.PRO_NAME from T_BASE_PROVINCE t2 where t2.PRO_ID = t1.PRO_ID) PRO_NAME 5 from T_BASE_CITY t1