例子：表名 Paper 。通过字段PaperID查找重复数据。
1 --查询某表中重复的数据
select * from Paper group by PaperID having count(*)>1;
2--删除重复行数，只剩不重复的记录（rowid为sqlite自带字段）
delete from Paper where Paper.rowid not in (select MAX(Paper.rowid) from Paper group by PaperID);