Decode will act as value by value substitution.
For every value of field, it will checks for a match in a series of
if/then tests.
Syntax: decode (value, if1, then1, if2, then2, ……. else);
Ex:
SQL> select sal, decode(sal,500,'Low',5000,'High','Medium') from emp;
SAL
DECODE
----- ---------
500 Low
2500
Medium
2000 Medium
3500 Medium
3000 Medium
5000 High
4000 Medium
5000 High
1800 Medium
1200 Medium
2000 Medium
2700 Medium
2200 Medium
3200 Medium
SQL> select decode(1,1,3), decode(1,2,3,4,4,6) from dual;
DECODE(1,1,3) DECODE(1,2,3,4,4,6)
-----------------
------------------------
3 6
Ø If the number
of parameters are odd and different then decode will display
nothing.
Ø If the number
of parameters are even and different then decode will display last
value.
Ø If all the
parameters are null then decode will display nothing.
Ø If all the
parameters are zeros then decode will display zero.
