找出具有二维的变量的唯一性

Question

我有一张表“生产”：

|company | Product | Model|   
A          Printer   1200
B          Lap       1100
C          PC        1500
C          Lap       1300
A          Printer   1800

我想找出只生产1种产品的公司，  这些模型的数量超过1个。

我尝试了很多。但我只选择公司产品1类型。

请帮助我。

Answer 1

试试这个：

Select company from production
group by company
having count(distinct product) = 1
and count(distinct model) > 1

在此处查看演示小提琴http://sqlfiddle.com/#!2/f8a11/3

Answer 2

select company from product 
where company in 
(select company from product group by company having count(distinct product)=1)
group by company 
having count(distinct model)>1

Answer 3

select company from production
group by company 
having count(distinct model)>1 and count(distinct product)=1