本文介绍了如何检查mysql表中多列的重复项的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有一张棒球运动员表(全部 1000 名左右)，有字段:
I have a table of baseball players(all 1000 or so), with fields:
mysql> describe person;
+-----------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| firstname | varchar(30) | NO | | NULL | |
| lastname | varchar(30) | NO | | NULL | |
+-----------+-------------+------+-----+---------+----------------+
但我认为有些球员已经被加入了两次.我如何检查并检查特定名字、姓氏组合出现的次数?
But I think there are some players that have gotten added in twice. How can I go through and check for how many occurrences of a particular firstname, lastname combo?
推荐答案
这提供了重复的列表:
SELECT firstname, lastname, COUNT(*)
FROM person
GROUP BY firstname, lastname
HAVING COUNT(*) > 1;
如果您想查看每一行的计数，请删除 have 子句:
If you want to see the counts for every row remove the having clause:
SELECT firstname, lastname, COUNT(*)
FROM person
GROUP BY firstname, lastname;
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