一：上码

--  查询生产最高速度的计算机(PC或便携式电脑)厂商，查询结果按照厂商升序排列-- 分析：1.从pc表和product表当中当中找到速度最快的 表1
--       2.从laptop表和product表当中找到速度最快的 表2
--       3.将表1和表2联合起来找速度最快的-- 1.
-- select maker,speed 
--       from pc,product
--       where pc.model = product.model
--       AND speed >= ALL(SELECT speed FROM pc);-- -- 2.
-- select maker,speed
--         from laptop,product
--         where product.model = laptop.model
--         and speed >= all(select speed from laptop);-- 3.
select maker from (select maker,speed from pc,productwhere pc.model = product.modelAND speed >= all(SELECT speed FROM pc)unionselect maker,speedfrom laptop,productwhere product.model = laptop.modeland speed >= all(select speed from laptop)) as temp1where temp1.speed >= all(select speed from (select maker,speed from pc,productwhere pc.model = product.modelAND speed >= all(SELECT speed FROM pc)unionselect maker,speedfrom laptop,productwhere product.model = laptop.modeland speed >= all(select speed from laptop))as temp2);