postgresql - 查找每个国家/地区的最小值和最大值

Question

我正在尝试寻找每个国家/地区数量最多和最少的经销商 两列分配器，具有最小数量和最大数量 我已经能够从其他帖子中获取信息，但它在一列中，但我希望它在每个国家/地区的行中

参见http://sqlfiddle.com/#!17/448f6/2

期望的结果

"country"   "min_qty_name"  "max_qty_name"
1. "Madagascar" "Leonard Cardenas" "Gwendolyn Mccarty"
2. "Malaysia"   "Arsenio Knowles" "Yael Carter" 
3. "Palau"      "Brittany Burris" "Clark Weaver"  
4. "Tanzania"   "Levi Douglas" "Levi Douglas"

Answer 1

您可以使用子查询:

select distinct country,
(select distributor_name 
 from product 
 where country = p.country 
 order by quantity limit 1) as min_qty_name,
 (select distributor_name 
 from product 
 where country = p.country 
 order by quantity desc limit 1) as max_qty_name
 from product p;

Fiddle