限制 SQL 查询中每个 id 的行数 [重复]

Posted 2023-02-16

【中文标题】限制 SQL 查询中每个 id 的行数 [重复]

【英文标题】：Limit number of rows per id in a SQL query [duplicate]

【发布时间】：2014-03-12 17:13:52

【问题描述】：

我想为每个品牌 ID 限制 10 个产品的结果。这是我的查询的样子：

SELECT 
products.id, products.brand_id
FROM products
  JOIN (
    select id, brand_id
    from products limit 10) 
    pinner ON products.id = pinner.id
WHERE pinner.brand_id IN ('1', '2','3') ;

这显然行不通。有什么建议吗？

编辑： 这篇文章帮助我解决了问题：http://www.xaprb.com/blog/2006/12/07/how-to-select-the-firstleastmax-row-per-group-in-sql/

【问题讨论】：

去掉子查询。添加 order by 子句。将限制条款放在最后。

【参考方案1】：

改编自另一个答案

  set @brand_id= '';
  set @num = 0;

  select
  products.id, products.brand_id,
  @num := if(@brand_id= brand_id, @num + 1, 1) as dummy_1,
  @brand_id:= brand_id as dummy_2,
  @num as row_number
  from products
  where brand_id IN ('1', '2','3')
  group by
  brand_id,
  row_number
  having row_number <= 10;

【参考方案2】：

这样试试

SET @rownum =0;

SELECT id,brand_id FROM
(
    SELECT 
    products.id, products.brand_id, @rownum := @rownum + 1 AS rank
    FROM products
      JOIN (
        SELECT id, brand_id
        from products limit 10) 
        pinner ON products.id = pinner.id
    WHERE pinner.brand_id IN ('1', '2','3') 
) AS T
Where rank < 10