Difference between CASE and DECODE

Question

Hi All,
Could you please explain me the basic differences between the CASE and DECODE, which performs fast...?
DECODE is Oracle one, and the CASE is ANSI standard.
As per my knowledge, CASE is a statement and DECODE is a function which was defined in the Standard package.
If we use DECODE, the package has to load first, so it will take a little longer than the CASE. CASE is a simple statement which is ANSI standard.
We can use the CASE in the where clause and can not use the DECODE in the where clause.
Please clarify me and correct me if anything wrong.
Thanks,

Answer 1

IMO, the main important point is the way CASE and DECODE handles NULL
SQL> select ename,comm,
  2         decode(comm,300,'A',null,'B','C') dcd,
  3         case comm when 300 then 'A'
  4                   when null then 'B'
  5                   else 'C'
  6         end cs
  7  from emp;
ENAME            COMM D C
SMITH                 B C --"DECODE treats NULL=NULL. But for CASE, NULL is not equal to "another" NULL
ALLEN             300 A A
WARD              500 C C
JONES                 B C
MARTIN           1400 C C
BLAKE                 B C
CLARK                 B C
SCOTT                 B C
KING                  B C
TURNER              0 C C
ADAMS                 B C
JAMES                 B C
FORD                  B C
MILLER                B C
14 rows selected.
{code}
Edited by: jeneesh on Jun 3, 2013 1:13 PM
Note: in CASE, you should use IS NULL
{code}
case when comm=300 then 'A'
       when comm is null then 'B'
      else 'C'
end
{code}