SQL and dates

Hi All,

I have a question relating to SQL and dates.  I have a database which contains a number of items.  Each time the program is executed, the database is checked to see if an item will be out of date within the next 21 days. The problem that I am having is this:  the query is not returning any items which exceed the date given.

Here is basically what I am doing:


SQL Statement (within the query):

Select * from ALL_ITEMS
where :ThisDate > Items_Date


the :ThisDate parameter is typed as a DateTime, as is the Items_Date


The procedure I am using to check these items is:

Procedure TMain.CheckDates;
Var Check_Date: TDateTime;

begin
   Check_Date := DATE + 21;  
   ItemQuery.Active := False;
   ItemQuery.ParamByName('ThisDate').asDataTime := ChecK_Date;
   ItemQuery.Active := True;
End;

Ok, from this, I get no records in the query at all.

Any ideas at all.  The program is in very early development stages, therefore, I am quite happy to change anything to get this thing working properly!

Thanks for any help you can provide.

Stuart.

If you have any examples, please forward them to jonstu@acay.com.au if possible.

OH!  And as a last second thought, any ideas how to make a Paradox database use full dates??  ie DD/MM/YYYY??.
LVL 6
Stuart_JohnsonAsked:
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kjtengConnect With a Mentor Commented:

     changing   ItemQuery.ParamByName('ThisDate').asDataTime to
       ItemQuery.ParamByName('ThisDate').asDatETime)

     May be there is really no record dated after 21 from today?
     Or may be what you actually want is the result for
        :ThisDate < Items_Date

     "to make a Paradox database use full dates"
     1. changes the short date format in your Windows Control Panel International
     dialog box.
      OR
     2. put the following line in you program:
          shortDateformat:= 'dd/mm/yyyy';

     Hope this help
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JaccoCommented:
What type of database do you use?

It is better to use Open and close:

ItemQuery.Close;
ItemQuery.ParamByName('THISDATE').AsDateTime := Check_Date;
ItemQuery.Open;

But your example should work as well.

How did you check if the Query returns data?

To make an easy check:
Add a TDataSource and set its DataSet property to ItemQuery
Add a DBGrid and set its DataSource property to the DataSource you just added.

If the Query is opened the data should automatically appear in the DBGrid.

Regards Jacco
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Stuart_JohnsonAuthor Commented:
Hi Jacco,

Thats basically how I am doing it now.  I just dont get any data.  I'll keep trying.  Thanks for the comment.  Any more suggestions??

Stu
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Stuart_JohnsonAuthor Commented:
Edited text of question
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vladikaCommented:
Try this
just interchange :ThisDate and Items_Date as

select * from ALL_ITEMS  where Items_Date<:ThisDate

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kjtengCommented:
I have tried your code. It works fine on my pc.(after changing   ItemQuery.ParamByName('ThisDate').asDataTime to
  ItemQuery.ParamByName('ThisDate').asDatETime)

May be there is really no record dated after 21 from today?
Or may be what you actually want is the result for
   :ThisDate < Items_Date

"to make a Paradox database use full dates"
1. changes the short date format in your Windows Control Panel International dialog box.
 OR
2. put the following line in you program:
     shortDateformat:= 'dd/mm/yyyy';

Hope this help


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Stuart_JohnsonAuthor Commented:
kjteng,

Can you please repost this as an answer for me.  I'll test this once I get home.  I think I have made a mistake :)  I didnt realise that  you could use the ShortDateFormat though.  Thanks for pointing that out.

Stuart.
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Stuart_JohnsonAuthor Commented:
Hi kjteng,

OK, I have it working now, thanks very much.  That ShortDateFormat constant would be very handy if it was documented :)  I couldnt find anything in any of the help files or examples relating to it at all.

The program is working just fine.  Thank you.  The points are well earnt!

Stuart.

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