SQL 如何删除特定列的重复行并保留一个

Question

下面的代码returns 列出了特定列的重复行。在这种情况下，我试图找到大学名称的重复项。我的问题是如何删除重复项并为每个不同的 university_name?

只保留一份副本

    Select * from `university` where `university_name` in ( select `university_name` from `university` group by `university_name` having count(*) > 1 )

这是结果：

你能解释一下我是 SQL 的新手吗！提前致谢！！

Answer 1

试试这个：

DELETE  u
FROM    university u
        LEFT JOIN
        (
            SELECT MIN(ID) ID, university_name
            FROM    university
            GROUP   BY university_name
        ) v ON  u.ID = v.ID AND
                u.university_name = v.university_name
WHERE   v.ID IS NULL

Answer 2

1) 如果要保留id值最小的行：

DELETE a
FROM university a, university b
WHERE a.id > b.id
AND  b.university_name=a.university_name

2) 如果要保留id值最高的行：

DELETE a
FROM university a, university b
WHERE a.id < b.id
AND  b.university_name=a.university_name

Answer 3

删除重复项并保留 ID 最旧的行

DELETE a
FROM university a
JOIN university b ON a.university_name = b.university_name
WHERE a.id > b.id

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