MySQL中刪除重復數據只保留一條

用SQL語句,刪除掉重復項只保留一條

在幾千條記錄里,存在着些相同的記錄,如何能用SQL語句,刪除掉重復的呢 
1、查找表中多余的重復記錄，重復記錄是根據單個字段（peopleId）來判斷

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

2、刪除表中多余的重復記錄，重復記錄是根據單個字段（peopleId）來判斷，只留有rowid最小的記錄

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、查找表中多余的重復記錄（多個字段）

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

4、刪除表中多余的重復記錄（多個字段），只留有rowid最小的記錄

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、查找表中多余的重復記錄（多個字段），不包含rowid最小的記錄

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.消除一個字段的左邊的第一位：

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

7.消除一個字段的右邊的第一位：

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

8.假刪除表中多余的重復記錄（多個字段），不包含rowid最小的記錄

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