MySQL中删除重复数据只保留一条 | 您所在的位置:网站首页 › sql删除重复值留一条记录 › 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
|
CopyRight 2018-2019 实验室设备网 版权所有 |