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