Incase if you want to check for all the columns then try this query:

delete from emp where rowid not in (select max(rowid) from emp group by id,name,no)

My emp table had 3 columns id,name,no and you need to group by all the columns in order to check if any column contains different value or not.if yes then that record will not be considered as duplicate and will not be deleted. The above query will delete the record only when all the columns have same value