The schema is SYSIBM.
The DAYS function returns an integer representation of a date.
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 (except DBCLOB), it is first converted to a character string before the function is executed.
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.
The result is 1 more than the number of days from January 1, 0001 to D, where D is the date that would occur if the DATE function were applied to the argument.
SELECT DAYS(PRENDATE) - DAYS(PRSTDATE)
INTO :EDUCATION_DAYS
FROM PROJECT
WHERE PROJNO = 'IF2000'
Results in EDUCATION_DAYS
being set to 396. SELECT SUM(DAYS(PRENDATE) - DAYS(PRSTDATE))
INTO :TOTAL_DAYS
FROM PROJECT
WHERE DEPTNO = 'E21'
Results in TOTAL_DAYS
being set to 1584 when using the sample table.