Deleting duplicate rows in the table

I am searching for a way to delete the duplicate records in a table..
Is anybody having efficient way to do it..?

The command is:

DELETE dv
FROM a WHERE rowid <
(SELECT MIN(rowid)
FROM b
WHERE a.dv = b.dv);

i.e. if the table name is emp and the dupicate column value is ename:

DELETE ename
FROM emp a
WHERE rowid <
(SELECT MIN(rowid)
FROM emp b
WHERE a.ename = b.ename)

Another solution is:

delete from where rowid not in (
select max(rowid) from group by );