SQL 选择计数最高的行

Question

我试图根据两个字段仅选择具有最高 COUNT() 的行。

首先，我有一个查询，该查询提供特定 ITEM-SUPPLIER 组合在我的表中出现了多少次的值。

select itemid, ordersupplierid, COUNT(OrderSupplierId) AS SupCount from purchaseorderline
group by itemid, ordersupplierid
order by ItemID

在我的结果中:

itemid   | ordersupplierid | SupCount
15850    |  579            |  1
15850    |  587            |  3
15850    |  605            |  2
15851    |  616            |  5
15852    |  579            |  1
15852    |  587            |  2
15854    |  616            |  11
15855    |  616            |  1

所以从那里我只需要获取行:

itemid   | ordersupplierid | SupCount
15850    |  587            |  3
15851    |  616            |  5
15852    |  587            |  2
15854    |  616            |  11
15855    |  616            |  1

如在具有最高 SupCount 的 ItemId - OrderSupplierId 组合中。

有人知道如何做到这一点吗？将不胜感激。

Answer 1

您可以使用窗口函数:

select itemid, ordersupplierid, supcount
from (select itemid, ordersupplierid, count(*) AS SupCount,
             max(count(*)) over (partition by itemid) as maxcount
      from purchaseorderline
      group by itemid, ordersupplierid
     ) io
where supcount = maxcount
order by ItemID;

如果有联系，那么这将返回所有匹配的行。如果您只想要一行(即使有并列)，那么您可以使用 row_number():

select itemid, ordersupplierid, supcount
from (select itemid, ordersupplierid, count(*) AS SupCount,
             row_number() over (partition by itemid order by count(*) desc) as seqnum
      from purchaseorderline
      group by itemid, ordersupplierid
     ) io
where seqnum = 1
order by ItemID;