WEEK_ISO

The WEEK_ISO function returns an integer between 1 and 53 that represents the week of the year. The week starts with Monday. Week 1 is the first week of the year to contain a Thursday, which is equivalent to the first week containing January 4. Thus, it is possible to have up to 3 days at the beginning of the year appear as the last week of the previous year or to have up to 3 days at the end of a year appear as the first week of the next year.

expression: An expression that returns a value of one of the following built-in data types: a date, a timestamp, a character string, or a graphic string.
If expression is a character or graphic string, its value must be a valid string representation of a date or timestamp. For the valid formats of string representations of dates and timestamps, see String representations of datetime values.

The result of the function is a large integer. If the argument can be null, the result can be null; if the argument is null, the result is the null value.

Examples

Using the PROJECT table, set the host variable WEEK (INTEGER) to the week that project (‘AD2100') ended.
```
  SELECT WEEK_ISO(PRENDATE)
    INTO :WEEK
    FROM PROJECT
    WHERE PROJNO = 'AD3100'
```
Results in WEEK being set to 5.

Assume that table X has a DATE column called DATE_1 with various dates from the list below.

  SELECT DATE_1, WEEK_ISO(DATE_1)
    FROM X

Results in the following:

  1997-12-28    52
  1997-12-31    1
  1998-01-01    1
  1999-01-01    53
  1999-01-04    1
  1999-12-31    52
  2000-01-01    52
  2000-01-03    1