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Re: Comparing Dates & Timestamps
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Re: Comparing Dates & Timestamps


  • Subject: Re: Comparing Dates & Timestamps
  • From: David Griffith <email@hidden>
  • Date: Fri, 12 Mar 2004 00:09:41 +0100

> On Mar 11, 2004, at 11:51 AM, David Griffith wrote:
>
>> I have
>> removed the Value Class (Obj-C) column, however is NSCalendarDate the
>> incorrect Value Class?  I actually looked it up earlier and noticed it
>> was
>> on Obj-C class.  That is the default that EOModeler gave me when I
>> select
>> internal type of Date.
>
> If I recall correctly, EOModeler stores "NSCalendarDate" in the
> eomodel, probably for historic reasons (Obj-C preceded Java as an EOF
> implementation language).  But for WO 5, an NSTimestamp is instantiated
> instead of an NSCalendarDate.  So as far as the eomodel is concerned,
> its contents are identical whether you display "Value Class (Obj-C)" or
> "Value Class" in EOModeler.
>
>> I am assuming this will give me timestamps for the current time today,
>> and
>> the same time yesterday.  I am looking for say a timestamp for today at
>> 00:00:00 and today at 23:59:59 (as I noticed suggested by Chuck in
>> another
>> post) but I'm not sure how to get that.
>
> You stated that you wanted to compare a Date column for equality.
> Because a Date doesn't include hours, minutes, and seconds, it doesn't
> matter that the NSTimestamps being used for comparisons include hours,
> minutes, and seconds.  There is only one Date between the current time
> today and that same time yesterday.  No need to do the extra work to
> set hours, minutes, and seconds to 0 (i.e., midnight).
>
Yes, I want to compare today's date against the date that was stored in the
database, which as I said is stored as an NSCalendarDate and in the database
it has the form "2004-03-11".  However, when I try and filter the list with:

NSTimestamp today = new NSTimestamp();
....
bindings.addObject(distributor);
bindings.addObject(today);
distQualifier = EOQualifier.qualifierWithQualifierFormat("distributor = %@
AND orderDateShipped= %@", bindings);

I get no results.  This has to be because of the timestamp having more info
I guess, since when I do the same thing but using, for example,
orderDateShipped <= %@

I get all results prior to the timestamp.


> There's also no need to use 23:59:59 for a comparison; in fact, it
> might not return the correct results in those databases that store time
> in millisecond precision.  To match all of today, "orderDate >=
> today_00:00:00 and orderDate < tomorrow_00:00:00" is more correct than
> "orderDate >= today_00:00:00 and orderDate <= today_23:59:59".
>
> Aloha,
> Art
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  • Follow-Ups:
    • Re: Comparing Dates & Timestamps
      • From: Art Isbell <email@hidden>
References: 
 >Re: Comparing Dates & Timestamps (From: Art Isbell <email@hidden>)

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