[英]Grouping Multiple Columns
我有以下查询:
SELECT od.product_id, od.product_name, od.product_quantity, od.product_price,
o.id_address_delivery, a.id_country, a.id_state, s.name
FROM `ps_order_detail` od
LEFT JOIN ps_orders AS o ON od.`id_order` = o.`id_order`
LEFT JOIN `ps_address` AS a ON o.`id_address_delivery` = a.`id_address`
LEFT JOIN `ps_state` AS s ON a.id_state = s.id_state
ORDER BY o.`date_add` DESC
LIMIT 100;
它在哪里返回数据,如下所示:
product_id | 产品名称| product_qty | 产品价格| id_state
我想知道每个州的畅销书。 例如:
状态A:最畅销产品是产品A(销售数量为500)国家B:最畅销产品是产品C(销售数量为150)国家C:最畅销产品是产品A(销售量为100)
目前,我正在考虑在两列之间进行JOIN操作,但是第二次想到这需要类似“枢轴”的功能。
我知道如何获取每种产品的总销量
SELECT od.product_id, od.product_name, COUNT(od.product_id) AS 'total'
FROM `ps_order_detail` od
GROUP BY od.product_id
ORDER BY od.product_id DESC
LIMIT 100;
我也知道每个州的总销售量,但是我不确定如何将两者结合起来以达到我的需求。 我将不胜感激。 谢谢
您需要汇总查询的分组最大数量。 您可以这样做,例如:
select state, product_name, quantity
from (
select id_state, state, product_id, product_name, quantity,
@grprow := (case when @grp = id_state then @grprow + 1 else 1 end) as grprow,
@grp := id_state
from (
SELECT a.id_state, max(s.name) as state, od.product_id,
max(od.product_name) as product_name,
sum(od.product_quantity) as quantity
FROM `ps_order_detail` od
LEFT JOIN ps_orders AS o ON od.`id_order` = o.`id_order`
LEFT JOIN `ps_address` AS a ON o.`id_address_delivery` = a.`id_address`
LEFT JOIN `ps_state` AS s ON a.id_state = s.id_state
group by a.id_state, od.product_id
) grped,
(select @grprow := 0, @grp := null) init
order by id_state, quantity desc, product_id
) grpmax
where grprow = 1
order by id_state;
它将对每个州和产品的数量求和,然后对每个州的结果编号,然后取第一个。 如果两种产品在一个状态中的数量相同,则仅采用其中一种(具有较低的product_id)。 如果您想同时拥有两者,则可以调整@grprow
的编号条件。
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