DateTime fields, methods over such fields, DateTime depended SQL where-clause and SQL-functions.

[Ivan Smahin]

Hello All,

     This is short info about usage of DateTime features in Valentina 2.

     1. There are three datetime types in Valentina 2:
        Date, Time and DateTime.

        As far as I know, storing milliseconds in time and datetime fields
        is new to version 1.

        Important feature is "year auto correction". It means you can set
        such database params as CenturyBound and Century for getting proper
        dates, putting ones in "short-year" forms.

        Also you can set own date and time separators and choose date format
        for comfortable usage. It is possible to change those params at any time.
        ( Please note - you should use current datetime format in any queries,
        expected values and methods' text. )


     2. "date", "time", "datetime" keywords. What is it for.
        Where it must be used and so on.

        The first two keywords are from SQL-92 standard, the third is Valentina
        SQL-syntax extension.

        You HAVE TO use these keywords in methods predicates
        in case you need to define datetime-literal.

        Example:
          There are samples of method's text:
                "fld1 <> date'2004-01-01'"
                "fld2 = time'16:00:00'"
                "fld3 < datetime'2004-01-01 01:00:00'"

        Also, you CAN use these keywords in any other places. For example:

        "YEAR(date'2004-01-01')"
        "... where fld1 > date'2004-01-01' "

        but

        "YEAR('2004-01-01')"
        "... where fld1 > '2004-01-01' "

        are also allowable.

        Strict usage of such keywords must be only in methods' predicates based on
        datetime-literals.

        
     3. There is powerful set of datetime SQL-functions in Valentina 2.
        I would say this is a most powerful set in DBMS world.
        
        
-- 
Best regards,
 Ivan                          mailto:IvanSmahin at public.kherson.ua