Update Statements in SQL

UPDATE:

Update emp set comm= sal*.10;

Update emp set comm= sal*.10 where deptno = 10;

Update emp a set comm= (select decode(b.loc, 'NEW YORK', 100, 200) from dept b where a.deptno = b.deptno);

update emp a set comm = a.sal*0.1 where exists(select 1 from dept d where a.deptno = d.deptno);

update emp set (ename, sal, comm, deptno, empno) =
(select b.ename,b.sal*1.10, b.comm, decode(b.deptno, 10, 20, 30), b.empno from emp1 b where
a.empno = b.empno);