根据 mysql 查询中的外键值获取特定类别的 2 条记录？

Question

我有两个 table product 和 mastercategory

产品有列

id - pk, 
title- varchar,
price - varchar,
selling_price - varchar, 
description - varchar, 
is_approved - bool,
is_live - bool,
is_visible - bool,
category_id - fk (foreign_key of category table)

mastercategory 有列

id - pk, 
name - varchar, 
is_active - bool,
is_hotcategory - bool,

我想获取每个类别的 2 条最新记录，其中 is_hotcategory 是 true

我怎样才能得到这个

我试过这个：

select cp.id,cp.title, cp.category_id from product cp 
left join mastercategory cmc on cp.category_id = cmc.id where cmc.is_hotcategory = 1 and cp.id in (
select max(cp.id) As id
from product cp 
where cp.is_visible = 1 and cp.is_live= 1 and cp.is_approved=1 
group by category_id 

union all

select max(cp.id) As id
from product cp 
left join mastercategory cmc on cp.category_id = cmc.id 
where cmc.is_hotcategory = 1 and 
cp.is_visible = 1 and cp.is_live= 1 and cp.is_approved=1 and
(cp.id not in (select max(cp.id) 
from product cp 
where cp.is_visible = 1 and cp.is_live= 1 and cp.is_approved=1 group by category_id )) group by category_id 
) order by category_id asc;

我正在获取每个类别的最后一条记录，然后获取每个类别的第二条最后记录，然后结合两个搜索查询

我认为它会起作用，但如果我必须获得每个类别的 2 条以上记录怎么办。还有其他解决办法吗？

Answer 1

WITH cte AS (
    select cp.id, cp.title, cp.category_id,
           ROW_NUMBER() OVER (PARTITION BY cp.category_id ORDER BY cp.id DESC) rn
    from product cp 
    join mastercategory cmc on cp.category_id = cmc.id 
    where cmc.is_hotcategory
      and cp.is_visible
      and cp.is_live
      and cp.is_approved 
)
SELECT *
FROM cte
WHERE rn < 3;

我假设“每个类别的最新记录”是具有相同category_id的行中具有最大id的产品行（我没有找到类似于[=13=的列]).如果不是，则相应地调整框架规格。

根据 mysql 查询中的外键值获取特定类别的 2 条记录？

Get 2 record of a particular category based on foreignkey value in mysql query?

mysql

sql