MySQL中删除重复数据只保留一条

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用 SQL 语句, 删除掉 MySQL 重复项只保留一条

在几千条记录里, 存在着些相同的记录, 如何能用 SQL 语句, 删除掉重复的呢
1、查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断

SELECT
    *
FROM
    people
WHERE
    peopleId IN (SELECT
            peopleId
        FROM
            people
        GROUP BY
            peopleId
        HAVING
            count(peopleId) > 1
    )

2、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有 rowid 最小的记录

DELETE
FROM
    people
WHERE
    peopleName IN (SELECT
            peopleName
        FROM
            people
        GROUP BY
            peopleName
        HAVING
            count(peopleName) > 1
    )
AND peopleId NOT IN (SELECT
        min(peopleId)
    FROM
        people
    GROUP BY
        peopleName
    HAVING
        count(peopleName) > 1
)

3、查找表中多余的重复记录（多个字段）

SELECT
    *
FROM
    vitae a
WHERE
    (a.peopleId, a.seq) IN (SELECT
            peopleId,
            seq
        FROM
            vitae
        GROUP BY
            peopleId,
            seq
        HAVING
            count(*) > 1
    )

4、删除表中多余的重复记录（多个字段），只留有 rowid 最小的记录

DELETE
FROM
    vitae a
WHERE
    (a.peopleId, a.seq) IN (SELECT
            peopleId,
            seq
        FROM
            vitae
        GROUP BY
            peopleId,
            seq
        HAVING
            count(*) > 1
    )
AND rowid NOT IN (SELECT
        min(rowid)
    FROM
        vitae
    GROUP BY
        peopleId,
        seq
    HAVING
        count(*) > 1
)

5、查找表中多余的重复记录（多个字段），不包含 rowid 最小的记录

SELECT
    *
FROM
    vitae a
WHERE
    (a.peopleId, a.seq) IN (SELECT
            peopleId,
            seq
        FROM
            vitae
        GROUP BY
            peopleId,
            seq
        HAVING
            count(*) > 1
    )
AND rowid NOT IN (SELECT
        min(rowid)
    FROM
        vitae
    GROUP BY
        peopleId,
        seq
    HAVING
        count(*) > 1
)

6. 消除一个字段的左边的第一位：

UPDATE tableName
SET [Title]= RIGHT ([Title],(len([ Title]) - 1))
WHERE
    Title LIKE '村 %'

7. 消除一个字段的右边的第一位：

UPDATE tableName
SET [Title]= LEFT ([Title],(len([ Title]) - 1))
WHERE
    Title LIKE '% 村'

8. 假删除表中多余的重复记录（多个字段），不包含 rowid 最小的记录

UPDATE vitae
SET ispass =- 1
WHERE
    peopleId IN (SELECT
            peopleId
        FROM
            vitae
        GROUP BY
            peopleId

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