Question

Delphi 7 :: TADO Dataset Filter Property :: Cast DateTime Field to Date

Asked by: Marius0188

Hi Experts,

I am using a TADOTable component.
In my database table I have a TDateTime field.

My idea is to filter all rows for a given date range by using the Filter property.
How would the syntax look for this as I would firstly need to cast the TDateTime field to TDate and then
specify the ranges.

In SQL it would have looked something like this:

SELECT * FROM TABLE1
WHERE
CAST(FLOOR(CAST(DateTimeFiled AS FLOAT)) AS DATETIME) > :DATE1
AND
CAST(FLOOR(CAST(DateTimeFiled AS FLOAT)) AS DATETIME) < :DATE2

Thanks!

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Asked On
2008-05-07 at 00:45:44ID23381896
Topics

Delphi Database

,

Delphi Programming

Participating Experts
2
Points
500
Comments
6

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Answers

 

by: rfwoolfPosted on 2008-05-07 at 00:54:39ID: 21513974

Hmm... sorry if I'm wrong, but with filtering I believe the dataset won't need you to cast it if the fieldtype is TDateTime as you say.
So try something like
Filtered := false;
Filter := 'DatetimeFiled > ' + QuotedStr(MyDate);
Filtered := true;

* Watch out for issues with date formats, i.e. on some systems 12/01/2000 is December 1st.

 

by: ziolkoPosted on 2008-05-07 at 00:58:54ID: 21513997

I'm not sure if Filter property supports that complex filter conditions, you can try:
ADOTable.Filtered := False;
ADOTable.Filter := Format('CAST(FLOOR(CAST(DateTimeFiled AS FLOAT)) AS DATETIME) > %s
AND
CAST(FLOOR(CAST(DateTimeFiled AS FLOAT)) AS DATETIME) < %s', [date1_as_string, date2_as_string]);
ADOTable.Filtered := True;

but I would rather expect it to crash on ADOTable.Open

I think in your case it would be better to use ADOQuery component instead of ADOTable, then you can use:

ADOQuery.SQL.Text := Format('SELECT * FROM TABLE1
WHERE
CAST(FLOOR(CAST(DateTimeFiled AS FLOAT)) AS DATETIME) > %s
AND
CAST(FLOOR(CAST(DateTimeFiled AS FLOAT)) AS DATETIME) < %s', [date1_as_string, date2_as_string]);

ziolko.

 

by: rfwoolfPosted on 2008-05-07 at 01:06:04ID: 21514030

Are you sure that casting is necessary?
If you have a TDateTime
like this 01/01/2000 10:15:00
and a TDate
like this 01/01/2000 00:00:00
then the following is true
the TDateTime > the TDate
and if you say
filter := 'MyDateField >= 01/01/2000'
...then 01/01/2000 10:15:00 will come up

 

by: Marius0188Posted on 2008-05-07 at 02:11:12ID: 21514435

Yup, sorry I actually did realize that I can encode the date time with the hour/sec/ms part
set to zeros which will give me the desired result I am looking for.

Thanks guys, will split the points. OK?

 

by: rfwoolfPosted on 2008-05-07 at 02:26:33ID: 21514511

Thanks.

>>"Yup, sorry I actually did realize that I can encode the date time with the hour/sec/ms part
set to zeros which will give me the desired result I am looking for."
Yes, but I think the point I was making is that a TDate is the equivalent of a TDateTime except TDate has 00:00:00 set for the time portion.
Therefore you can do comparisons with TDate and TDatetime.
If you're interested you can run this test, although things might differ when using a filter :)
var
  MyDateTime : TDatetime;
  MyDate : TDate;
begin
  MyDateTime := EncodeDateTime(2000, 02, 29, 12, 34, 56, 789);
  MyDate := EncodeDate(2000,02,29);
  //Note the ">=" part on the next line
  if MyDateTime >= MyDate then showmessage('true'); //should return true
end;

 

by: ziolkoPosted on 2008-05-07 at 02:35:51ID: 21514573

>>Thanks guys, will split the points. OK?

fine by me:)

ziolko.

20120131-EE-VQP-002

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