update (select e.ename emp_ename,d.ename dept_ename from e1 e,dept1 d
where d.deptno=e.deptno) set dept_ename=emp_ename;

create table e1 as select * from emp 
where rowid in(select max(rowid) from emp group  by deptno);

alter table e1 add constraint id_must_be_unique unique(deptno);

select * from e1;

create table dept1 as select * from dept;

select a.object_name, b.oracle_username, b.os_user_name,c.sid, c.serial#,c.terminal, d.sql_text
from sys.dba_objects a,
v$locked_object b,
v$session c,
v$sqltext d
where a.object_id = b.object_id
and c.sid = b.session_id
and c.sql_hash_value = d.hash_value

alter system kill session 'c.sid, c.serial#';