【2019年8月版】OCP 071认证考试原题-第38题

choose two.

You need to calculate the number of days from 1st January 2019 until today.

Dates are stored in the default format of DD-MON-RR.

Which two queries give the required output?

A) SELECT SYSDATE - TO_DATE (' 01-JANUARY-2019' ) FROM DUAL;

B) SELECT TO_DATE (SYSDATE, ' DD/MONTH/YYYY' ) - '01/JANUARY/2019' FROM DUAL;

C) SELECT ROUND (SYSDATE - TO_DATE(' 01/JANUARY/2019' ) ) FROM DUAL;

D) SELECT TO_CHAR (SYSDATE, ' DD-MON-YYYY') - '01-JAN-2019' FROM DUAL;

E) SELECT ROUND (SYSDATE- '01-JAN-2019') FROM DUAL:

Answer：AC

(解析：在进行日期计算的时候需要用转换函数把字符型的转换成日期型，oracle 不会隐式转换。)

来源：https://my.oschina.net/u/3902946/blog/3134172