sql查詢——子查詢

-- 子查詢
      -- 一句查詢語句內，再套一句查詢語句 ，叫子查詢
      -- 查詢班級類身高最高的人的名字
      select name from students where high=(select max(high) from students);
      select id as "序號", name as "姓名",high as "身高" from students where high=(select max(high) from students) order by id desc;
      -- 查詢省份下的所有區市，不知道省份的id
      select name from china pid=(select id from china where name="四川省");