Question

假设我有以下customer_offer表。

我的问题是：

如何选择键在该表中重复的所有行？

+---------+-------------+------------+----------+--------+---------------------+
| link_id | customer_id | partner_id | offer_id | key    | date_updated        |
+---------+-------------+------------+----------+--------+---------------------+
|       1 |          99 |         11 |       14 | mmmmmq | 2011-09-21 12:40:46 |
|       2 |         100 |         11 |       14 | qmmmmq | 2011-09-21 12:40:46 |
|       3 |         101 |         11 |       14 | 8mmmmq | 2011-09-21 12:40:46 |
|       4 |          99 |         11 |       14 | Dmmmmq | 2011-09-21 12:59:28 |
|       5 |         100 |         11 |       14 | Nmmmmq | 2011-09-21 12:59:28 |
+---------+-------------+------------+----------+--------+---------------------+

UPDATE：

非常感谢您的回答。有很多答案都很好。现在我得到了解决方案。

Answer 1

select * 
from customer_offer 
where key in 
(select key from customer_offer group by key having count(*) > 1)

<强>更新正如@ Scorpi0所提到的，如果使用大表，最好使用join。从mysql6.0开始，新的优化器会将这种子查询转换为连接。

Answer 2

Self join

SELECT * FROM customer_offer c1 inner join customer_offer c2
on c1.key = c2.key

或group by字段然后在count > 1

时占用

SELECT COUNT(key),link_id FROM customer_offer c1
group by key, link_id
having COUNT(Key) > 1

Answer 3

SELECT DISTINCT c1.* 
FROM customer_offer c1 
    INNER JOIN customer_offer c2
        ON c1.key = c2.key
        AND c1.link_id != c2.link_id

假设link_id是主键。

Answer 4

mysql网站上有许多线程解释了如何执行此操作。此链接将解释如何使用mysql执行此操作：http://forums.mysql.com/read.php?10,180556,180567#msg-180567

作为一个简短的例子，下面的代码来自链接，略有修改，更适合您的示例。

SELECT *
FROM tbl
GROUP BY key
HAVING COUNT(key)>1;

您还可以使用我喜欢的方法的joing，因为这会删除较慢的count方法：

SELECT * 
FROM this_table t 
inner join this_table t1 on t.key = t1.key

Answer 5

使用子查询进行计数检查，使用主查询选择行。计数检查查询只是：

SELECT `link_id` FROM `customer_offer` GROUP BY `key` HAVING COUNT(`key`) > 1

然后外部查询将通过加入它来使用它：

SELECT customer_offer.* FROM customer_offer
INNER JOIN (SELECT `link_id` FROM `customer_offer` GROUP BY `key` HAVING COUNT(`key`) > 1) AS count_check
ON customer_offer.link_id = count_check.link_id

Answer 6

SELECT link_id, key, count(key) as Occurrences 
FROM table 
GROUP BY key
HAVING COUNT(key)>1;

选择mysql中重复的字段

UPDATE：

6 个答案: