Question

我正在尝试编写我的第一个mySQL查询。如果行具有相同的article-number字段，我需要删除它们。我写了这个问题：

    SELECT
    article_number, COUNT(*)
FROM
    article_numbers
GROUP BY
    article_number
HAVING 
    COUNT(*) > 1

它显示了所有重复的行。但是如何为每个副本删除除1之外的所有内容？

由于

编辑：

我尝试了这个查询：

delete article_numbers from article_numbers inner join 
    (select  article_number
     from article_numbers 
     group by article_number
     having count(1) > 1) as duplicates
   on (duplicates.article_number = article_numbers.article_number)

但它给了我这个错误：

无法删除或更新父行：外键约束失败（api。products，CONSTRAINT products_article_number_id_foreign FOREIGN KEY（article_number_id）参考article_numbers （id））

编辑2：

我暂时禁用了外键，现在我的删除查询有效。但是如何修改它不会删除其中一个重复的行？

Answer 1

使用CROSS JOIN。

<强>查询

delete t1
from article_numbers t1,
article_numbers t2
where t1.id > t2.id 
and t1.article_number = t2.article_number;

Fiddle demo

Answer 2

我使用一个相当简单的查询来删除欺骗：

;WITH DEDUPE AS (
SELECT ROW_NUMBER() OVER(
    PARTITION BY article_number
        ORDER BY (SELECT 1)) AS RN
FROM article_numbers)
DELETE FROM DEDUPE
WHERE RN != 1

Answer 3

Delete c
from (select *,rank() over(order by article_number) as r  from article_numbers )c
where c.r!=1

Answer 4

如果存在相同的article_number但存在更高的ID，则删除一行：

delete from article_numbers t1
where exists (select 1 from article_numbers t2
              where t2.article_number = t1.article_number
                and t2.id > t1.id)

核心ANSI SQL，所以我认为它适用于MySQL和SQL Server。

Answer 5

我认为这会有所帮助：

    WITH tblTemp as
    (
    SELECT ROW_NUMBER() Over(PARTITION BY Name,Department ORDER BY Name)
       As RowNumber,* FROM <table_name>
    )
    DELETE FROM tblTemp where RowNumber >1

Answer 6

我修改了我的查询，我认为它现在有效：

SET FOREIGN_KEY_CHECKS=0;
delete article_numbers from article_numbers inner join 
    (select  min(id) minid, article_number
     from article_numbers 
     group by article_number
     having count(1) > 1) as duplicates
   on (duplicates.article_number = article_numbers.article_number and duplicates.minid <> article_numbers.id)

但似乎非常复杂。我会检查@Ullas方法，看它是否也有效。

删除mySQL表中的重复项

6 个答案: