当前位置：文江博客话题详情

如何从一张表中只获取重复的数据？

发布于 2024-12-03 16:49:21 字数 48 浏览 0 评论 0原文

我有一张表和许多数据，例如重复值和单个值。但我只想获取重复值数据，而不是单个值。

原文

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

往事风中埋 2024-12-10 16:49:21

SELECT columnWithDuplicates, count(*) FROM myTable
GROUP BY columnWithDuplicates HAVING (count(*) > 1);

SELECT columnWithDuplicates, count(*) FROM myTable
GROUP BY columnWithDuplicates HAVING (count(*) > 1);

回复收藏 0 原文

灯角 2024-12-10 16:49:21

上面的查询将显示重复的值。一旦您将其提供给业务用户，他们的下一个问题将是发生了什么？这些是怎么到那里的？重复项有模式吗？通常更能提供信息的是查看包含这些值的整行，以帮助确定为什么存在重复项。

-- this query finds all the values in T that
-- exist in the derived table D where D is the list of
-- all the values in columnWithDuplicates that occur more than once
SELECT DISTINCT
    T.* 
FROM
    myTable T 
    INNER JOIN 
    (
        -- this identifies the duplicated values
        -- courtesy of Brian Roach
        SELECT 
            columnWithDuplicates
        ,   count(*) AS rowCount
        FROM 
            myTable 
        GROUP BY 
            columnWithDuplicates 
        HAVING 
            (count(*) > 1)
    ) D 
        ON D.columnWithDuplicates = T.columnWithDuplicates

The above query will show the duplicated values. And once you provide that to a business user, their next question will be what happened? How did these get there? Is there a pattern to the duplicates? What's often more informative is to see the whole rows containing those values to help determine why there are duplicates.

-- this query finds all the values in T that
-- exist in the derived table D where D is the list of
-- all the values in columnWithDuplicates that occur more than once
SELECT DISTINCT
    T.* 
FROM
    myTable T 
    INNER JOIN 
    (
        -- this identifies the duplicated values
        -- courtesy of Brian Roach
        SELECT 
            columnWithDuplicates
        ,   count(*) AS rowCount
        FROM 
            myTable 
        GROUP BY 
            columnWithDuplicates 
        HAVING 
            (count(*) > 1)
    ) D 
        ON D.columnWithDuplicates = T.columnWithDuplicates

回复收藏 0 原文

~没有更多了~