下面的代码将找到所有使用了不止一次的product_id。每个product_id只能得到一条记录。

SELECT product_id FROM oc_product_reward GROUP BY product_id HAVING count( product_id ) >1

代码取自:http://chandreshrana.blogspot.in/2014/12/find-duplicate-records-based-on-any.html

SELECT DISTINCT a.email FROM `users` a LEFT JOIN `users` b ON a.email = b.email WHERE a.id != b.id;

要查找Employee中的name列中有多少记录是重复的，下面的查询很有用;

Select name from employee group by name having count(*)>1;

我的最后一个查询在这里合并了一些有用的答案-组合group by, count和GROUP_CONCAT。

SELECT GROUP_CONCAT(id), `magento_simple`, COUNT(*) c 
FROM product_variant 
GROUP BY `magento_simple` HAVING c > 1;

这提供了两个示例的id(逗号分隔)、我需要的条形码以及重复的数量。

相应地更改表和列。

SELECT 
    t.*,
    (SELECT COUNT(*) FROM city AS tt WHERE tt.name=t.name) AS count 
FROM `city` AS t 
WHERE 
    (SELECT count(*) FROM city AS tt WHERE tt.name=t.name) > 1 ORDER BY count DESC

SELECT ColumnA, COUNT( * )
FROM Table
GROUP BY ColumnA
HAVING COUNT( * ) > 1