在MYSQL中,如何按列值分隔这些分组数据?
我有一个具有以下结构的表:在MYSQL中,如何按列值分隔这些分组数据?,mysql,sql,join,group-by,Mysql,Sql,Join,Group By,我有一个具有以下结构的表: SELECT * FROM logs WHERE data = "Map load" ORDER BY timestamp DESC LIMIT 5 user_id timestamp data 3 2017-03-29 18:11:25 Map load 2 2017-03-29 18:10:11 Map load 5 2017-03-29 18:02:07 Map load 5 201
SELECT * FROM logs WHERE data = "Map load"
ORDER BY timestamp DESC LIMIT 5
user_id timestamp data
3 2017-03-29 18:11:25 Map load
2 2017-03-29 18:10:11 Map load
5 2017-03-29 18:02:07 Map load
5 2017-03-29 17:48:03 Map load
3 2017-03-29 17:38:48 Map load
我希望按15分钟的间隔将行分组,我已经这样做了。
但是,我还需要按用户id对这些数据进行分段
按间隔分组:
SELECT FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP(timestamp)/900)*900) AS `Time`,
COUNT(*) AS `Map Load` FROM logs
WHERE data = "Map load"
GROUP BY `Time` ORDER BY `Time` DESC LIMIT 3
Time Map Load
2017-03-29 18:00:00 3
2017-03-29 17:45:00 1
2017-03-29 17:30:00 1
预期结果布局:
Time user_id=3 user_id=2 user_id=5
2017-03-29 18:00:00 1 1 1
2017-03-29 17:45:00 0 0 1
2017-03-29 17:30:00 1 0 0
我还有其他60个用户,因此除了在15分钟间隔时间戳上为每个用户id加入此表的副本外,还有其他方法可以做到这一点吗?您可以使用条件聚合:
select FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP(timestamp) / 900) * 900) as time,
sum(user_id = 3) as User_id_3,
sum(user_id = 2) as User_id_2,
sum(user_id = 5) as User_id_5
from logs
where data = "Map load"
group by time
order by time desc LIMIT 3
如果用户数量较多,最好不要在SQL中透视值,而是在应用程序代码中透视值:
select FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP(timestamp) / 900) * 900) as time,
user_id,
count(*) as cnt
from logs l
join (
select FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP(timestamp) / 900) * 900) as time
from logs
group by time
order by time desc limit 3
) t on FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP(timestamp) / 900) * 900) = t.time
where data = 'Map load'
group by time,
user_id
order by time desc;
这很好,但是对于60多个用户来说,随着更多用户的加入,线性增长的查询是否明智?我不确定这将是可维护的,除非有一种方法,我可以为每个用户的id生成<代码>从用户中选择用户id@Lawrence_1718-在这种情况下,不要在SQL中透视表数据。在应用程序代码中执行此操作。也更新了答案。谢谢你的建议,但我现在没有太多的选择,已经生成的数据需要这个,不过谢谢你的帮助!