这是什么SQL查询? [英] What is the sql query for this?

问题描述

Id  Project_Id       Activity_Time        Username
1      100        2008-01-01 11:12:13         A
2      100        2008-01-01 00:00:00         B
3      500        2008-02-01 00:00:00         C
4      300        2008-02-03 00:00:00         D
5      500        2008-03-03 11:11:11         A
6      300        2008-04-04 00:00:00         D
7      500        2008-05-05 00:00:00         C
8      200        2008-06-06 00:00:00         D
9      100        2009-01-01 11:12:13         A
10     300        2010-01-01 01:02:03         A

根据以下输入选择 Project_Id 的sql查询是什么:

What is the sql query to select Project_Id based on following input :

1. 对于给定的用户名
2. 按Activity_Time排序-最新的
3. 与众不同的Project_Id
4. 仅10行

我尝试了几个查询，但没有任何效果，因此请在这里寻求帮助. 目前使用的是H2数据库，但是会在一段时间内发生变化.

I tried few queries nothing worked, so seeking help here. Currently H2 database is used but it would change over a period.

[更新]这是真正的项目要求，不是家庭作业，是新手，请不要取笑，要学习这些东西.

[Update] This is a true project requirement, not a home work, am a newbie, please don't make fun, am learning the stuffs.

推荐答案

如果不能完全正常工作，这应该是一个好的开始...

This should be a good start if not completely working ...

SELECT TOP 10 
    project_ID, max(activity_time) as activity_time
FROM
    table_name
WHERE
    username = usernameVariable
GROUP BY 
    project_id
ORDER BY 
    activity_time DESC

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