49、(11-1) choose the best answer
Examine the structure of the SHIPMENTS table:
You want to generate a report that displays the PO_ID and the penalty amount to be paid(罚款数额) if the SHIPMENT_DATE is later than one month from the PO_DATE. The penalty is $20 per day.
Evaluate the following two queries:
SQL> SELECT po_id, CASE
WHEN MONTHS_BETWEEN (shipment_date,po_date)>1 THEN
TO_CHAR((shipment_date - po_date)*20) ELSE 'No Penalty' END PENALTY
FROM shipments;
SQL>SELECT po_id, DECODE
(MONTHS_BETWEEN(po_date,shipment_date)>1,
TO_CHAR((shipment_date - po_date) * 20, 'NO Penalty') PENALTY
FROM shipments;
Which statement is true regarding the above commands?
A) Only the second query executes successfully but gives a wrong result.
B) Only the second query executes successfully and gives the correct result.
C) Only the first query executes successfully but gives a wrong result.
D) Both execute successfully and give correct results.
E) Only the first query executes successfully and gives the correct result.
Answer：E
(解析：decode 函数的语法是，decode(条件,值 1,返回值 1,值 2,返回值 2,...值 n,返回值 n,缺省值)，
所以不能有>1 的条件判断。原来 051 的题。
该语句可以改写为下面的语句：
SELECT empno,hiredate,
CASE
WHEN MONTHS_BETWEEN (sysdate,hiredate)>1
THEN TO_CHAR((sysdate - hiredate )*20)
ELSE 'No Penalty'
END PENALTY
FROM emp;)