Oracle decode用法

decode用法如下
select decode(3,1,'a',2,'b',3,'c','f') from dual;
結果為：c

與switch case概念相同
switch(3)
{
  case: 1
    console.write("a");
    break;
  case: 2
    console.write("b");
    break;
  case: 3
    console.write("c");
    break;
  default:
    console.write("f");
    break;
}