ocp 11g考試題庫詳解：1Z0-051-088題
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88. You need to calculate the number of days from 1st January 2007 till date.
Dates are stored in the default format of dd-mon-rr.
Which SQL statements would give the required output? (Choose two .)
A. SELECT SYSDATE - '01-JAN-2007' FROM DUAL;
B. SELECT SYSDATE - TO_DATE('01/JANUARY/2007') FROM DUAL;
C. SELECT SYSDATE - TO_DATE('01-JANUARY-2007') FROM DUAL;
D. SELECT TO_CHAR(SYSDATE, 'DD-MON-YYYY') - '01-JAN-2007' FROM DUAL;
E. SELECT TO_DATE(SYSDATE, 'DD/MONTH/YYYY') - '01/JANUARY/2007' FROM DUAL;
Answer: BC
試題解析：
日期與字符串做表達式計算，隱式將日期轉換為字符串，而字符串之間不能相減，所以ADE都是字符之間相減，所以錯誤。
BC之間相減是日期與日期之間的減，得出數字，是正確的。
