选择 sql 查询的前 10 行和后 10 行

Question

你好，我有一个这样的 sqlite 数据库

price   category_id product_id
100000  89  1
2000    88  2
50000   89  3

我想为每个类别提取产品id的前5个和后5个（每个类别的最高和最低产品）

我已经写好了

SELECT *
FROM sql_data_users.products
GROUP BY product_id,category_id
ORDER BY price ASC
LIMIT 10

但它给了我 10 行而不是 10*len(category_id) 为了使解决方案完整，我想添加另一个查询并将顺序更改为 ASC，然后将 2 个查询联合起来，这可能吗？如何实现？

Answer 1

你会使用窗口函数：

select t.*
from (select t.*,
             row_number() over (partition by category order by price asc) as seqnum_asc,
             row_number() over (partition by category order by price desc) as seqnum_desc
      from t
     ) t
where seqnum_asc <= 5 or seqnum_desc <= 5
order by category, price desc;