Question

*编辑：我正在使用sqlite3

我有一个包含3个表的数据库;电脑，笔记本和打印机。除了其他之外，他们还有列模型和价格。我试图从任何表格中选择最高价格的模型。我的尝试引导我：

select model
from
    (select model, max(price)
     from 
        (select model, price
         from laptop
         union all
         select model, price
         from printer
         union all
         select model, price
         from pc));

这给了我所有表中的最后一个模型。但是，如果我这样做：

select model, p
from
    (select model, max(price) as p
     from 
        (select model, price
         from laptop
         union all
         select model, price
         from printer
         union all
         select model, price
         from pc));

它给了我正确的结果，但我也坚持了价格。我不明白这是怎么可能的。

Answer 1

这应该做你想做的事情，并且还会带回关系：

select x.model
  from (select model, price
          from laptop
        union all
        select model, price
          from printer
        union all
        select model, price
          from pc) x
  join (select max(max_price) as max_price
          from (select max(price) as max_price
                  from laptop
                union all
                select max(price)
                  from printer
                union all
                select max(price)
                  from pc)) y
    on x.price = y.max_price

无法从多个表中查找最大值

1 个答案: