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*FROMpeopleWHEREpeopleId IN (SELECTpeopleIdFROMpeopleGROUP BYpeopleIdHAVINGcount(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
DELETEFROMpeopleWHEREpeopleName IN (SELECTpeopleNameFROMpeopleGROUP BYpeopleNameHAVINGcount(peopleName) > 1)AND peopleId NOT IN (SELECTmin(peopleId)FROMpeopleGROUP BYpeopleNameHAVINGcount(peopleName) > 1)
3、查找表中多余的重复记录（多个字段）
SELECT*FROMvitae aWHERE(a.peopleId, a.seq) IN (SELECTpeopleId,seqFROMvitaeGROUP BYpeopleId,seqHAVINGcount(*) > 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
DELETEFROMvitae aWHERE(a.peopleId, a.seq) IN (SELECTpeopleId,seqFROMvitaeGROUP BYpeopleId,seqHAVINGcount(*) > 1)AND rowid NOT IN (SELECTmin(rowid)FROMvitaeGROUP BYpeopleId,seqHAVINGcount(*) > 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*FROMvitae aWHERE(a.peopleId, a.seq) IN (SELECTpeopleId,seqFROMvitaeGROUP BYpeopleId,seqHAVINGcount(*) > 1)AND rowid NOT IN (SELECTmin(rowid)FROMvitaeGROUP BYpeopleId,seqHAVINGcount(*) > 1)
6.消除一个字段的左边的第一位：
UPDATE tableNameSET [ Title ]= RIGHT ([ Title ],(len([ Title ]) - 1))WHERETitle LIKE '村%'
7.消除一个字段的右边的第一位：
UPDATE tableNameSET [ Title ]= LEFT ([ Title ],(len([ Title ]) - 1))WHERETitle 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 vitaeSET ispass =- 1WHEREpeopleId IN (SELECTpeopleIdFROMvitaeGROUP BYpeopleId
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