选择MySQL数据库中单个列上具有最大值的行
我有一个名为NetLogs的MySQL表选择MySQL数据库中单个列上具有最大值的行,mysql,sql,Mysql,Sql,我有一个名为NetLogs的MySQL表 servername , session , label , occurence | Nost | 11973 | Unknown | 1 | | Nost | 11976 | Scan | 74 | | Nost | 11976 | Unknown | 35 | | Gold | 11998 | Attack | 1 | 我需要去 Nost
servername , session , label , occurence
| Nost | 11973 | Unknown | 1 |
| Nost | 11976 | Scan | 74 |
| Nost | 11976 | Unknown | 35 |
| Gold | 11998 | Attack | 1 |
我需要去
Nost | 11973|unknown|1|
Nost| 11976 |Scan | 74|
Gold|11998|Attack|1|
结果,
我试过:
select t1.* from NetLogs t1 left join NetLogs t2
on t1.servername=t2.servername and t1.session=t2.session and t1.occurence < t2.occurence
where t2.occurence is null;
但我得到错误1137-无法重新打开表
我也会满足于同样的结果,而不考虑最后发生的次数
所以下面的一些解决方案对我不起作用,所以我将表重新制作为常规表,而不是临时表,它们起作用了,这让我觉得我可能曾经有过一个工作查询,但由于我在临时表上运行它,所以得到了错误
这正是我想要的:
从NetLogs a中选择a.*,其中a.occurrence=从NetLogs b中选择Maxoccurrence,其中a.session=b.session和a.serverName=b.serverName
SELECT a.*
FROM NetLogs a
INNER JOIN
(
SELECT session, MAX(occurence) occurence
FROM NetLogs
GROUP BY session
) b ON a.session = b.session AND
a.occurence = b.occurence
另一方面,
SELECT a.*
FROM NetLogs a
WHERE a.occurence =
(
SELECT MAX(occurence) occurence
FROM NetLogs b
WHERE a.session = b.session
)
查询:
可能重复的
SELECT a.servername,
a.session,
a.label,
a.occurence
FROM NetLogs a
LEFT JOIN NetLogs b
ON b.session = a.session
AND a.occurence < b.occurence
WHERE b.session IS NULL
| SERVERNAME | SESSION | LABEL | OCCURENCE |
|------------|---------|---------|-----------|
| Nost | 11973 | Unknown | 1 |
| Nost | 11976 | Scan | 74 |
| Gold | 11998 | Attack | 1 |