Hello

If you want to use select statement in decode function

Given one example below.

Hope this will help you.

create table emp
(empno number,
ename varchar2(30),
status varchar2(10)
)
create or replace view empview(empno,ename,status,result)
as
select empno,ename,status,
decode((select status from emp a
where empno = b.empno),
'Male','Y',
'Female','N') result
from emp b