WEEK

The WEEK function returns an integer between 1 and 54 that represents the week of the year. The week starts with Sunday, and January 1 is always in the first week.

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.

Example

Using the PROJECT table, set the host variable WEEK (INTEGER) to the week that project (‘PL2100') ended.
```
  SELECT WEEK(PRENDATE)
    INTO :WEEK
    FROM PROJECT
    WHERE PROJNO = 'PL2100'
```
Results in WEEK being set to 38.

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

  SELECT DATE_1, WEEK(DATE_1)
    FROM X

Results in the following list shows what is returned by the WEEK function for various dates.

  1997-12-28    53
  1997-12-31    53
  1998-01-01    1
  1999-01-01    1
  1999-01-04    2
  1999-12-31    53
  2000-01-01    1
  2000-01-03    2