使用MySQL查找最新的重复ID
作者:互联网
我习惯做
SELECT email, COUNT(email) AS occurences
FROM wineries
GROUP BY email
HAVING (COUNT(email) > 1);
根据他们的电子邮件查找重复项.
但现在我需要他们的ID才能定义哪一个要删除.
第二个约束是:我只想要LAST INSERTED重复项.
因此,如果将2个条目与test@test.com作为电子邮件,并且它们的ID分别为40和12782,则它将仅删除12782条目并保留40条.
有关如何做到这一点的任何想法?我一直在捣碎SQL大约一个小时,似乎无法确切地找到如何做到这一点.
感谢,并有一个愉快的一天!
解决方法:
好吧,你有点回答你的问题.你似乎想要max(id):
SELECT email, COUNT(email) AS occurences, max(id)
FROM wineries
GROUP BY email
HAVING (COUNT(email) > 1);
您可以使用该语句删除其他人.使用连接删除有一个棘手的语法,您必须首先列出表名,然后使用连接指定from子句:
delete wineries
from wineries join
(select email, max(id) as maxid
from wineries
group by email
having count(*) > 1
) we
on we.email = wineries.email and
wineries.id < we.maxid;
或者将其写为exists子句:
delete from wineries
where exists (select 1
from (select email, max(id) as maxid
from wineries
group by email
) we
where we.email = wineries.email and wineries.id < we.maxid
)
标签:mysql,sql,duplicate-removal,duplicates 来源: https://codeday.me/bug/20190517/1121967.html