Question

我正在查询我的在线商店，我正在使用一个小组并通过查看产品delivery_format字段来计算DVD订单的订单数量。

以下是查询：

SELECT 
      account_asset.product_group_id,
      product_group.product_code,
      product_group.name,
      product_group.conference_year,
      product_group.delivery_format,
      product_group.id,
      count(*) AS myCount
  FROM account_asset
  INNER JOIN product_group ON product_group.id = account_asset.product_group_id
  GROUP BY account_asset.product_group_id
  ORDER BY product_group.conference_year,
         product_group.product_code,
         myCount

如何在'myCount'字段中获得总和？

Answer 1

从该结果集中选择：

select sum (mycount)
from
(select 
account_asset.product_group_id,
product_group.product_code, 
product_group.name,
product_group.conference_year,
product_group.delivery_format,
product_group.id,
count(*) as myCount
from account_asset 
inner join product_group ON product_group.id = account_asset.product_group_id
group by account_asset.product_group_id 
order by product_group.conference_year,product_group.product_code,myCount) T1

Answer 2

仅供参考：您不能通过别名来订购，就像您尝试使用ORDER BY MyCount一样。见下面的更正。

关于你的问题，我假设你想要每行的总数。所以这样做：

SELECT account_asset.product_group_id,
       product_group.product_code,
       product_group.name,
       product_group.conference_year,
       product_group.delivery_format,
       product_group.id,
       count(1) AS myCount,
       SUM((SELECT COUNT(1) FROM account_asset INNER JOIN product_group ON product_group.id = account_asset.product_group_id)) AS MyTotal
FROM account_asset
INNER JOIN product_group
    ON product_group.id = account_asset.product_group_id
GROUP BY account_asset.product_group_id
ORDER BY product_group.conference_year,
         product_group.product_code,
         count(1)

但是，在存储过程中定义变量要好得多，因为上面的内容可能会重新计算每一行（检查查询计划）。

所以，在sproc中这样做：

DECLARE @Total = (SELECT COUNT(1) FROM account_asset INNER JOIN product_group ON product_group.id = account_asset.product_group_id)

SELECT account_asset.product_group_id,
       product_group.product_code,
       product_group.name,
       product_group.conference_year,
       product_group.delivery_format,
       product_group.id,
       count(1) AS myCount,
       @Total AS myTotal
FROM account_asset
INNER JOIN product_group
    ON product_group.id = account_asset.product_group_id
GROUP BY account_asset.product_group_id
ORDER BY product_group.conference_year,
         product_group.product_code,
         count(1)

另外......如果你想让它更有效，可以将计算总数的查询更改为半连接而不是连接。即。使用相关的子查询。它的速度要快得多，因为您所做的只是检查product_group中是否存在account_asset。

     SELECT COUNT(1)
     FROM account_asset a WHERE EXISTS (SELECT 1 FROM product_group p WHERE p.id = a.product_group_id)

在连接中获取Sum并按查询分组

2 个答案: