Oracle-Decode()函数和CASE语句的比较

SELECT CASE SIGN(5 - 5)
            WHEN 1  THEN        'Is Positive'
            WHEN -1  THEN    'Is Negative'
            ELSE    'Is Zero'   END
FROM   DUAL;

if (SIGN(5 – 5) = 1) {
'Is Positive';
} else if (SIGN(5 – 5) = 2 ) {
'Is Negative';
}else {
‘Is Zero’
}

SELECT DECODE(SIGN(5 – 5), 1, 
'Is Positive', -1, 'Is Negative', ‘Is Zero’)
FROM　DUAL

switch ( SIGN(5 – 5) )
 {
   case 1 :  'Is Positive';  break;
   case 2 :  'Is Negative'; break;
   default :  ‘Is Zero’
}

SELECT CASE X-FIELD 
    WHEN  X-FIELD < 40  THEN ‘X-FIELD < 40’
    WHEN  X-FIELD < 50  THEN ‘X-FIELD < 50’
    WHEN  X-FIELD < 60  THEN ‘X-FIELD < 60’
    ELSE ‘UNBEKNOWN’END
FROM DUAL