oracle周数计算方法

从星期天开始起算

   Function Fn_GetWeekbyDate(P_Date Varchar2) Return Varchar2
   Is
   Begin
      Return To_char(To_Date(P_Date,'yyyy-mm-dd'),'fmww');
   End Fn_GetWeekbyDate;

从星期一开始起算

   Function Fn_GetWeekbyDate(P_Date Varchar2) Return Varchar2
   Is
   Begin
      Return To_char(To_Date(P_Date,'yyyy-mm-dd'),'fmiw');
   End Fn_GetWeekbyDate;

下面是一个有效参数列表to_char函数是用来转换为一个字符串的日期。这些参数可用于在多种组合。

Parameter	Explanation
YEAR	Year, spelled out
YYYY	4-digit year
YYY YY Y	Last 3, 2, or 1 digit(s) of year.
IYY IY I	Last 3, 2, or 1 digit(s) of ISO year.
IYYY	4-digit year based on the ISO standard
Q	Quarter of year (1, 2, 3, 4; JAN-MAR = 1).
MM	Month (01-12; JAN = 01).
MON	Abbreviated name of month.
MONTH	Name of month, padded with blanks to length of 9 characters.
RM	Roman numeral month (I-XII; JAN = I).
WW	Week of year (1-53) where week 1 starts on the first day of the year and continues to the seventh day of the year.
W	Week of month (1-5) where week 1 starts on the first day of the month and ends on the seventh.
IW	Week of year (1-52 or 1-53) based on the ISO standard.
D	Day of week (1-7).
DAY	Name of day.
DD	Day of month (1-31).
DDD	Day of year (1-366).
DY	Abbreviated name of day.
J	Julian day; the number of days since January 1, 4712 BC.
HH	Hour of day (1-12).
HH12	Hour of day (1-12).
HH24	Hour of day (0-23).
MI	Minute (0-59).
SS	Second (0-59).
SSSSS	Seconds past midnight (0-86399).
FF	Fractional seconds.