how to delete duplicate values from a table?

102.

delete from tablename t where rowid<>(select max(rowid) from tablename t2 where t.columname=t2.columnname)

delete from tablename t where rowid<(select max(rowid) from tablename t2 where t.columname=t2.columnname

delete from tablename t where rowid>(select max(rowid) from tablename t2 where t.columname=t2.columnname

this is used for deleting duplicate values from table