【071题库】最新OCP-071考试题库解析-第47题
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071题库-第47题、choose two
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 two SQL statements would give the required output?
A) SELECT TO_DATE (SYSDATE, 'DD/MONTH/YYYY') - '01/JANUARY/2007' FROM DUAL;
B) SELECT SYSDATE - TO_DATE ('01/JANUARY/2007') FROM DUAL;
C) SELECT SYSDATE -'01-JAN-2007' FROM DUAL;
D) SELECT SYSDATE - TO_DATE ('01-JANUARY-2007') FROM DUAL;
E) SELECT TO_CHAR (SYSDATE, 'DD-MOM-YYYY') - '01-JAN-2007' FROM DUAL;
Answer:BD
(解析：对数据进行混合运算时必须要用转换函数转换为日期格式，因为它不会隐式转换，但是我们在insert
数据时，会实现隐式转换。
SQL> SELECT SYSDATE - TO_DATE ('01-1 月-2007') FROM DUAL;
或者：
SQL> SELECT SYSDATE - TO_DATE ('01/1 月/2007') FROM DUAL;
)
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