MySQL中删除重复数据只保留一条

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
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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