SELECT bank_name, decode(bank_id, 001, 'SBI', 002, 'ICICI', 003, 'dena', 'Gateway') result FROM banks;

decode(
bank_id, 
001, 'SBI', 
002, 'ICICI', 
003, 'dena', 
'Gateway')

IF bank_id = 001 THEN
   result := 'SBI';
 
ELSIF bank_id = 002 THEN
   result := 'ICICI';
 
ELSIF bank_id = 003 THEN
   result := 'Dena';
 
ELSE
   result := 'Gateway';
 
END IF;