NLS_DATE_LANGUAGEE和NLS_DATE_FORMAT

通過(guò)一道051的考題看這兩個(gè)默認(rèn)參數(shù)的用法：

91.View the Exhibit and examine the structure of the PROMOTIONS table. Which two SQL statements would execute successfully?

A.UPDATE promotions SET promo_cost = promo_cost+ 100 WHERE TO_CHAR(promo_end_date, 'yyyy') > '2000';
B.SELECT promo_begin_date FROM promotions WHERE TO_CHAR(promo_begin_date,'mon dd yy')='jul 01 98';
C.UPDATE promotions SET promo_cost = promo_cost+ 100 WHERE promo_end_date > TO_DATE(SUBSTR('01-JAN-2000',8));
D.SELECT TO_CHAR(promo_begin_date,'dd/month') FROM promotions WHERE promo_begin_date IN (TO_DATE('JUN 01 98'), TO_DATE('JUL 01 98'));
答案：AB
A:正確
B:正確
C:錯(cuò)誤
D:錯(cuò)誤
C和D的錯(cuò)誤都是因?yàn)闆](méi)有指定轉(zhuǎn)換的格式，而默認(rèn)的格式是通過(guò)

NLS_DATE_LANGUAGEE和NLS_DATE_FORMAT決定的，因此他們都存在問(wèn)題，可以進(jìn)行如下修改

SQL> select TO_DATE(SUBSTR('01-JAN-2000',8)) from dual;
select TO_DATE(SUBSTR('01-JAN-2000',8)) from dual
ORA-01861: 文字與格式字符串不匹配
SQL> alter session set NLS_DATE_FORMAT='yyyy';
Session altered

SQL> select TO_DATE(SUBSTR('01-JAN-2000',8)) from dual;
TO_DATE(SUBSTR('01-JAN-2000',8
------------------------------
2000/12/1

SQL> select TO_DATE('JUN 01 98') from dual;
select TO_DATE('JUN 01 98') from dual
ORA-01841: (完整) 年份值必須介于 -4713 和 +9999 之間, 且不為 0

SQL> alter session set NLS_DATE_FORMAT='MON DD RR';
Session altered

SQL> alter SESSION SET NLS_DATE_LANGUAGE='AMERICAN';
Session altered

SQL> select TO_DATE('JUN 01 98') from dual;
TO_DATE('JUN0198')
------------------
1998/6/1