Question

我有一个services表，在MySQL数据库上有以下列行

`id`    `service_rendered`  `created_at`
 1       repair              2016-11-19 14:40:56
 2       install             2016-11-19 14:40:58
 3       repair              2016-11-19 14:44:27
 4       install             2016-11-19 14:50:35

我正在尝试计算服务的数量以及它呈现的最后日期/时间。列created_at是日期时间类型。

我正在运行的SQL语句是：

SELECT COUNT(`service_rendered`) as `count_service`, `service_rendered`, `created_at` as `last_rendered`
FROM services
WHERE `id` IN (1,2,3)
GROUP BY `service_rendered`
ORDER BY `created_at` DESC

但我得到的是：

`count_service`    `service_rendered`  `last_rendered`
 2                  repair              2016-11-19 14:40:56
 1                  install             2016-11-19 14:40:58

如何编写我的SQL以便能够在2016-11-19 14:44:27修复？

Answer 1

您可以使用created_at列上的MAX使用以下解决方案：

SELECT COUNT(`service_rendered`) AS `count_service`, `service_rendered`, MAX(`created_at`) AS `last_rendered`
FROM services
WHERE `id` IN (1,2,3)
GROUP BY `service_rendered`
ORDER BY `last_rendered` DESC

演示： http://sqlfiddle.com/#!9/3906b7/2

您想要ORDER BY created_at DESC？

您必须使用列last_rendered的别名，因此请将ORDER BY created DESC替换为ORDER BY last_rendered DESC

Answer 2

您必须为max(created_date)选择created_date而不是last_rendered。然后您的查询将变为

select 
    count(service_rendered) as count_service,
    service_rendered,
    max(created_at) as last_rendered
from
    services
group by service_rendered
order by created_at desc

SQL Group By Order BY在datetime列上降序

2 个答案: