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 peopleWHERE peopleId IN (

SELECT peopleId

FROM people

GROUPBY peopleId

HAVINGcount(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

DELETEFROM peopleWHERE peopleName IN (

SELECT peopleName

FROM people

GROUPBY peopleName

HAVINGcount(peopleName)>1 )ANDpeopleIdNOTIN (

SELECTmin(peopleId)

FROM people

GROUPBY peopleName

HAVINGcount(peopleName)>1)

3、查找表中多余的重复记录（多个字段）

SELECT*FROM vitae aWHERE (a.peopleId, a.seq) IN (

SELECT peopleId,

seq

FROM vitae

GROUPBY peopleId,

seq

HAVINGcount(*)>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

DELETEFROM vitae aWHERE (a.peopleId, a.seq) IN (

SELECT peopleId,

seq

FROM vitae

GROUPBY peopleId,

seq

HAVINGcount(*)>1 )ANDrowidNOTIN (

SELECTmin(rowid)

FROM vitae

GROUPBY peopleId,

seq

HAVINGcount(*)>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 aWHERE (a.peopleId, a.seq) IN (

SELECT peopleId,

seq

FROM vitae

GROUPBY peopleId,

seq

HAVINGcount(*)>1 )ANDrowidNOTIN (

SELECTmin(rowid)

FROM vitae

GROUPBY peopleId,

seq

HAVINGcount(*)>1)

6.消除一个字段的左边的第一位：

UPDATE tableNameSET[ 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 tableNameSET[ 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 vitaeSETispass=-1WHERE peopleId IN (

SELECT peopleId

FROM vitae

GROUPBY peopleId