WEEK_ISO scalar function

The schema is SYSFUN.

The WEEK_ISO function returns the week of the year of the argument as an integer value in the range 1-53. The week starts with Monday and always includes 7 days. Week 1 is the first week of the year to contain a Thursday, which is equivalent to the first week containing January 4. It is therefore possible to have up to 3 days at the beginning of a year appear in the last week of the previous year. Conversely, up to 3 days at the end of a year may appear in the first week of the next year.

The argument must be a DATE, TIMESTAMP, or a valid character string representation of a date or timestamp that is not a CLOB. In a Unicode database, if a supplied argument is a graphic string, it is first converted to a character string before the function is executed.

The result of the function is INTEGER. The result can be null; if the argument is null, the result is the null value.

Example

DATE       WEEK_ISO    DAYOFWEEK_ISO
---------- ----------- -------------
1997-12-28          52             7
1997-12-31           1             3
1998-01-01           1             4
1999-01-01          53             5
1999-01-04           1             1
1999-12-31          52             5
2000-01-01          52             6
2000-01-03           1             1