大数据就业实战培训 Oracle就业实战培训
OCP 19c 1Z0-082认证考试题库（第4题）-CUUG内部学员版082题库解析
4.Which two statements are true about date/time functions in a session where NLS_DATE_FORMAT is set to DD-MON-YYYY HH24:MI:SS? (Choose two.)
A. CURRENT_TIMESTAMP returns the same date and time as SYSDATE with additional details of fractional seconds
B. SYSDATE can be queried only from the DUAL table
C. CURRENT_DATE returns the current date and time as per the session time zone
D. SYSDATE can be used in expressions only if the default date format is DD-MON-RR
E. SYSDATE and CURRENT_DATE return the current date and time set for the operating system of the database server
F. CURRENT_TIMESTAMP returns the same date as CURRENT_DATE
Answer: CE
(解析：dual 只是一个为了语法完整设计的虚拟的表，这些函数都可以基于某张表进行执行。CURRENT_TIMESTAMP 返回的信息是最多的，包含时区信息。)
SQL> select CURRENT_TIMESTAMP from dual;
CURRENT_TIMESTAMP
---------------------------------------------------------------------------
14-JUL-20 02.52.00.783461 PM +08:00
SQL> select sysdate from dual;
SYSDATE
--------------------
14-JUL-2020 15:23:32
SQL> select sysdate from emp;
SYSDATE
--------------------
14-JUL-2020 15:24:31
