Decode statement

[Shestakov]

Example:

ccreate table test_decode(a date, b number);
insert into test_decode (a, b) values(trunc(sysdate-5),1);
insert into test_decode (a, b) values(trunc(sysdate+5),2);
insert into test_decode (a, b) values(to_date(null),3);

SQL> select sysdate, a, b, decode(a,null,'X',decode(sign(a-sysdate),-1,'X','Y'))
from test_decode;
  2  
SYSDATE   A		     B D
--------- --------- ---------- -
18-NOV-02 23-NOV-02	     2 Y
18-NOV-02		     3 X
18-NOV-02 13-NOV-02	     1 X