Q: 90 For which two actions can you use the TO_DATE function? (Choose two.)
A. convert any date literal to a date
B. convert any numeric literal to a date
C. convert any date to a character literal
D. format 'January 10 1999' for input
E. format '10-JAN-99' to 'January 10 1999'
Answer: A, D
题目答案为什么是A D呢? B,C,E错在哪里呢？
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感觉LZ都没看oracle入门的内容，上来就直接背题库。
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我看你问的这几个问题，都是oracle的基础知识。稍稍看看书就能作答，你在这提问等人回答，不如翻翻书来的快。
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TO_DATE
1.转换一种时间格式为另外一种时间格式.
2.转换合法的时间字符串为时间.
例如:
- SQL code
1. MONTHS_BETWEEN with to_date function SQL>SQL> SELECT MONTHS_BETWEEN(TO_DATE('22SEP2006','ddMONyyyy'), 2 TO_DATE('13OCT2001','ddMONyyyy')) "Months difference" 3 FROM dual;Months difference----------------- 59.2903226SQL>SQL>SQL>2. Converting spelled date to DATE format SQL>SQL> -- Converting spelled date to DATE format.SQL> SELECT TO_DATE('January 15','MONTH DD') "Sample" from DUAL;Sample---------15-JAN-06SQL>3. Converting number representation to DATE format SQL>SQL> -- Converting number representation to DATE format.SQL> SELECT TO_DATE('061167','MMDDYY') "Birthday" from DUAL;Birthday---------11-JUN-67SQL>4. TO_CHAR(TO_DATE('04-JUL-15', 'DD-MON-YY'), 'DD-MON-YYYY') SQL>SQL> SELECT TO_CHAR(TO_DATE('04-JUL-15', 'DD-MON-YY'), 'DD-MON-YYYY'), 2 TO_CHAR(TO_DATE('04-JUL-75', 'DD-MON-YY'), 'DD-MON-YYYY') 3 FROM dual;TO_CHAR(TO_ TO_CHAR(TO_----------- -----------04-JUL-2015 04-JUL-2075SQL> 5. TO_DATE('04-JUL-15', 'DD-MON-RR'): Uses the RR format when interpreting the years 15 and 75 SQL>SQL> --Uses the RR format when interpreting the years 15 and 75SQL>SQL> SELECT 2 TO_CHAR(TO_DATE('04-JUL-15', 'DD-MON-RR'), 'DD-MON-YYYY'), 3 TO_CHAR(TO_DATE('04-JUL-75', 'DD-MON-RR'), 'DD-MON-YYYY') 4 FROM dual;TO_CHAR(TO_ TO_CHAR(TO_----------- -----------04-JUL-2015 04-JUL-1975SQL>
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B. convert any numeric literal to a date
numeric literal是字符化的数字,这里只有当数字与日期格式匹配才能正确转换,而不能是any
C. convert any date to a character literal
只能用to_char把日期转换成文字
E. format '10-JAN-99' to 'January 10 1999'
后面一个日期不是标准日期格式
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