Question

我正在努力纠正SQL命令以获取以下前10个名称（使用标准SQL，不能使用TOP）以实现以下两种关系：

      Orders (customer_email, item_id, date)
      Items(id, name, store, price)

关于如何做到这一点的任何建议？我想我需要对它们进行分组，但是我该如何根据计数来获得前10个分组呢？

Answer 1

select *
  from (select x.*, row_number() over(order by num_orders desc) as rn
          from (select i.name, count(*) as num_orders
                  from orders o
                  join items i
                    on o.item_id = i.id
                 group by i.name) x) x
 where rn <= 10

Answer 2

SELECT 
    COUNT(*) count_per_item
  , i.id
  , i.name
FROM   
    Orders o 
JOIN   
    Items i 
ON  (o.item_id = i.id)
GROUP BY
    i.id
  , i.name 
ORDER BY
    count_per_item DESC 
LIMIT 10;

SQL查询来自两个关系的前10个项目

2 个答案: