ORACLE常见函数

to_char函数
to_char(WFSJ,''yyyy-mm-dd hh24:mi:ss'') 返回后面的格式

to_char(1210.73, '9999.9')      return '1210.7'
to_char(1210.73, '9,999.99')    return '1,210.73'
to_char(1210.73, '$9,999.00')   return '$1,210.73'
to_char(21, '000099')           return '000021'

如：
SQL> select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual;

TO_CHAR(SYSDATE,'YY
-------------------
2009-09-25 09:25:49

 

add_months函数：在现在时间上加上多少个月

当前日期为：2009-09-25

SQL> select to_char(add_months(sysdate,1),'yyyy-mm-dd hh24:mi:ss') from dual;

TO_CHAR(ADD_MONTHS(
-------------------
2009-10-25 09:31:37

 

to_date函数：把字符串转化为日期类型
如：
SQL> select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE
= American') from dual;

TO_CHAR(T
---------
monday

SQL> select to_char(to_date('2009-09-25','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE
= American') from dual;

TO_CHAR(T
---------
friday

months_between函数

SQL> select months_between('19-12月-1999','19-3月-1999') mon_between from dual;

MON_BETWEEN
-----------
          9

SQL> select months_between('19-3月-1999','19-12月-1999') mon_between from dual;

MON_BETWEEN
-----------
         -9