[英]Get the latest data of duplicated entries in MYSQL
I have a mysql table that contains all the subscribed plan by users. 我有一个mysql表,其中包含用户的所有预订计划。 I am trying to create a SELECT statement that will allow me to select for a particular user from the table. 我正在尝试创建一个SELECT语句,该语句将允许我从表中选择特定用户。 Also, if that user have duplicated entries, it will get the latest date of all. 同样,如果该用户有重复的条目,它将获得所有的最新日期。
For example, I want to look for John from the table and the date I should get is 2015-09-10. 例如,我想从表中查找John,我应该得到的日期是2015-09-10。
Subscribed table
ID FirstName Date
-------------------------------
1 John 2015-05-30
2 Mary 2014-01-10
3 John 2015-09-10
4 John 2015-03-15
5 Loen 2013-12-11
How should I go about creating the SELECT statement to above the result? 我应该如何在结果上方创建SELECT语句?
If you just need the first one, you can use LIMIT
in conjunction with ORDER BY
: 如果只需要第一个,则可以将LIMIT
与ORDER BY
结合使用:
SELECT * FROM `Subscribed`
WHERE `FirstName` = 'John' -- Get the name John.
ORDER BY `Date` DESC -- Sort results in descending order by Date.
LIMIT 1 -- Limit the results to one.
The result will be ordered by date in descending order, and the LIMIT 1
gives out the first row. 结果将按日期降序排列,并且LIMIT 1
给出第一行。
Or to be precise, you can also use Grouping Functions if you need more than one row. 确切地说,如果需要多个行,也可以使用分组功能。
SELECT `FirstName`, MAX(`Date`) FROM `Subscribed`
WHERE `FirstName` = 'John'
GROUP BY `FirstName`
Fiddle: http://www.sqlfiddle.com/#!9/ebb90/1 小提琴: http ://www.sqlfiddle.com/#!9 / ebb90 /1
Try this 尝试这个
SELECT FirstName, max(Date) FROM yourTable
WHERE FirstName = 'John'
also you can use group by
to take the result for all persons not just John
您也可以使用group by
为所有人获取结果,而不仅仅是John
If you want to do this for all users: 如果要对所有用户执行此操作:
select s.*
from subscribed s join
(select firstname, max(date) as maxd
from subscribed
group by firstname
) ss
on ss.firstname = s.firstname and ss.maxd = s.date;
Query for required output: 查询所需的输出:
SELECT * FROM (SELECT * FROM `Subscribed`
ORDER BY `DATE` DESC) t group by firstName
Alternatively, you can use MAX and GROUP BY 或者,您可以使用MAX和GROUP BY
SELECT firstName, MAX(date) FROM `Subscribed`
group by firstName
Verify output here : http://www.sqlfiddle.com/#!9/ec5d1/1 在此处验证输出: http : //www.sqlfiddle.com/#!9/ec5d1/1
Output: 输出:
id firstName date
3 John September, 10 2015 00:00:00
2 Mary January, 10 2014 00:00:00
Gordeon Linoff has good answer, if your ID is a primary key and always grow on time as well, you can do this SQL for better speed: Gordeon Linoff有一个很好的答案,如果您的ID是主键并且总是按时增长,则可以执行以下SQL以获得更快的速度:
SELECT s.*
FROM subscribed s,
(SELECT FirstName, max(ID) maxID FROM subscribed GROUP BY 1) AS ss
WHERE s.ID = ss.maxID;
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