mysql - 除最新记录外的组行数

Question

我可以有一个 group by 子句，它以这个查询运行的方式返回每个组的最新记录:

select `id`, `user_id`, `type`, `product_id`
    from `table` where `id` in 
        (select max(`id`) from `table` where `product_id`=1 group by `type`)
order by `id` group by `type`

但我也希望在正常的 group by 查询中计算每个组中的行数。

+----------+-------------------------------------------------+
|   type   | select count(1) where type=:type group by type; |
+----------+-------------------------------------------------+
|   one    |                        5                        |
+----------+-------------------------------------------------+
|   two    |                        1                        |
+----------+-------------------------------------------------+
|   three  |                        109                      |
+----------+-------------------------------------------------+

是否也可以有这些数字？

Answer 1

您可以使用 JOIN 来完成:

SELECT t.id,t.user_id,t.type,t.product_id,s.cnt
FROM YourTable t
INNER JOIN (SELECT p.type,max(p.id) as max_id,count(*) as cnt
            FROM YourTable p
            WHERE p.product_id = 1
            GROUP BY p.type) s
 ON(t.id = s.max_id)
WHERE t.product_id = 1

现在派生表 s 将包含每个 type 的 max(id) 和 count ，通过加入它，它将过滤所有其他记录。