informix到oracle移植---函数

   infomrix                   oracle                                                                             说明
month(date_expr)       to_number(to_char(date_expr,’MM’))                            返回相应月份
time                            to_char(sysdate,’hh24:mi:ss’)                                          返回当前时间
today                          sysdate                                                                           返回当前系统时间
weekday(date_expr)   to_number(to_char(date_expr,’D’)-1)                             返回指定日期是星期几，0表
示星期日
year(date_expr)          to_number(to_char(date_expr,’YYYY’))                        返回指定日期对应

str[index1,index2]      substr(str,index1,len)                                                         Index1和index2在Informix中必须是常
量，而Oracle中index1,len可以是变量
downshift(str)              lower(str)                                                                        返回小写字符串
upshit(str)                   upper(str)                                                                        返回大写字符串
length(str)                    length(str)                                                                        返回字符串长度
current                        sysdate                                                                            返回当前日期和时间
date(“12/13/1999”)    to_date(‘12/13/1999’, ’mm/dd/yyyy’)                              返回指定格式日期
day(dtime_expr)          to_number(to_char(dtime_expr,’dd’))                              返回指定日期是某月的第几天
extend(value[,first to last])  to_date(to_char(value, ’formate-mask’))                   调整日期时间精度