MySQL中删除重复数据只保留一条

Posted 2020-09-23 竹山一叶

用SQL语句,删除掉重复项只保留一条

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
        HAVINGcount(peopleId) > 1
    )
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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

DELETEFROM
    people
WHERE
    peopleName IN (
        SELECT
            peopleName
        FROM
            people
        GROUP BY
            peopleName
        HAVINGcount(peopleName) > 1
    )
AND peopleId NOT IN (
    SELECTmin(peopleId)
    FROM
        people
    GROUP BY
        peopleName
    HAVINGcount(peopleName) > 1
)
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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
        HAVINGcount(*) > 1
    )
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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

DELETEFROM
    vitae a
WHERE
    (a.peopleId, a.seq) IN (
        SELECT
            peopleId,
            seq
        FROM
            vitae
        GROUP BY
            peopleId,
            seq
        HAVINGcount(*) > 1
    )
AND rowid NOT IN (
    SELECTmin(rowid)
    FROM
        vitae
    GROUP BY
        peopleId,
        seq
    HAVINGcount(*) > 1
)
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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
        HAVINGcount(*) > 1
    )
AND rowid NOT IN (
    SELECTmin(rowid)
    FROM
        vitae
    GROUP BY
        peopleId,
        seq
    HAVINGcount(*) > 1
)
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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%‘
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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‘
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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 =- 1WHERE
    peopleId IN (
        SELECT
            peopleId
        FROM
            vitae
        GROUP BY
            peopleId

来源： http://blog.csdn.net/z_youarethebest/article/details/53785435

来自为知笔记(Wiz)