C / C++ / MFC

3-Dec-02 22:48

hello,

i have an mfc program and an access database. i connected them with odbc.
how can i make the following sql statement in my mfc programm?

select distinct xy from mytable

i want to read out 'xy' from a table 'mytable' and put these CString into a ComboBox:

Now i tried this:

<br />
CMyDatabase db;<br />
db.Open( CRecordset::dynaset,<br />
_T( "Select distinct xy from mytable" ) );<br />
<br />
db.MoveFirst();<br />
while(!db.IsEOF())<br />
{<br />
m_ctrlCombo.AddString(db.m_xy);<br />
db.MoveNext();<br />
}<br />
db.Close();<br />
UpdateData(false);<br />

i get the error, when i want to use this funktion. the error:

error with the call of a data record

what´s wrong????? Unsure | :~

thanks
mfc

Alexandru Savescu3-Dec-02 23:03

3-Dec-02 23:03

You need to follow these steps:

1. Open the database (using most likely a DSN, or a connection string).

2. Create a CRecordset object that uses the above open datastring.

3. Open the CRecordset object with a SQL query ("SELECT disintct...")

4. Once the recordset is open, iterate through recordset via MoveNext, MoveFirst etc.

Also, is wise to include everything in a try/catch block and you will most likely catch a pointer to CDBException object.

Best regards,
Alexandru Savescu

P.S. Interested in art? Visit this!

MFC is the Best3-Dec-02 23:59

3-Dec-02 23:59

thanks for reply.

i tried your idea:

	<br />
CMyDatabase db;<br />
db.Open();<br />
CRecordset rs (&db);<br />

but i get an error. must i include something (i included

#include "afxdb.h"
)?

thanks
mfc

Alexandru Savescu4-Dec-02 1:12

4-Dec-02 1:12

afxdb is a standard header, so you should use angle brackets:

#include <afxdb.h>

Best regards,
Alexandru Savescu

P.S. Interested in art? Visit this!

MFC is the Best4-Dec-02 1:20

4-Dec-02 1:20

yes, i use angle brackets (< >).....but it does not work.

why? can you help me????

the error is here

<br />
CRecordset rs(&db);<br />

the program has problems with &db

why?
mfc

Alexandru Savescu4-Dec-02 1:26

4-Dec-02 1:26

Please tell us what your error is. Apparently afxdb is enough standard to include.

Best regards,
Alexandru Savescu

P.S. Interested in art? Visit this!

MFC is the Best4-Dec-02 1:34

4-Dec-02 1:34

okay...first the code:

<br />
CMyDatabase db;<br />
db.Open();<br />
CRecordset rs (&db);<br />

the error:

'CRecordset::CRecordset':Conversion parameter 1 from 'class CMyDatabase *' in 'class CDatabase *' not possible.

what´s wrong?

thanks
mfc

Alexandru Savescu4-Dec-02 2:03

4-Dec-02 2:03

Here's what's going on:

1. It has nothing to do with any header file.

2. Why do you use a CMyDatabase object? Are you overriding some functionality of the CDatabase class?

3. If you are using a custom database object (CMyDatabase) make sure it is derived from CDatabase.

Voila!

Best regards,
Alexandru Savescu

P.S. Interested in art? Visit this!

MFC is the Best4-Dec-02 2:14

4-Dec-02 2:14

i understand. my database object is derived from CRecordset.

isn´t there a possiblity to make the sql statement:

select distinct xy from mytable

with a database object from CRecordset?
Because i ever use CRecordset.... Unsure | :~

thank you very much Rose | [Rose]

mfc

Alexandru Savescu4-Dec-02 3:10

4-Dec-02 3:10

No.

You are making a fundamental confustion. A database consists of tables and when you retrieve a record you read data from one/or more table(s) from the database.

MFC ODBC classes are: CDatabase that wrapps around a database and CRecordset the wrapps around a table (or more tables).

If you want to make a SELECT DISTINCT xy FROM MyTable you have to create a database object that opens the database MyTable table is in, then you create a CRecordset object that takes a pointer to a CDatabase and you pass the SQL statement to that CRecordset (or CRecordset-derived) object. Then you can navigate via MoveNext, MoveLast etc. through the database.

You can, however, execut SQL commands to the database objects. These are generally DELETE or INSERT statements (but not SELECT):

CDatabase db;
db.Open (...);
CString MyDelStr = _T ("DELETE FROM MyTable");
db.ExecuteSQL (MyDelStr);

CString MyInsertStr = _T ("INSERT INTO MyTable Values.....");
db.ExecuteSQL (MyInsertStr);

I hope I've been helpful!

Best regards,
Alexandru Savescu

P.S. Interested in art? Visit this!

MFC is the Best4-Dec-02 8:32

4-Dec-02 8:32

thank you very very much..... Rose | [Rose]

i tried your idea....

<br />
CDatabase db;<br />
db.Open(_T( "Datenbank" ), FALSE,FALSE, _T( "ODBC"));<br />
CRecordset rs(&db);<br />
rs.Open(CRecordset::forwardOnly ,"Select distinct xy from Mytable");<br />

i connectet access and vc++ with ODBC. the ODBC driver from my database i namend: 'Datenbank'.
in my database i have different tables and one is called xy.

in my code (above) must be a mistake....it doesnt work...why? Unsure | :~

how can i get the strings which i read out of my database table?

thank you.
mfc

drawing shapes over DirectShow

Tony Fontenot4-Dec-02 4:14

Tony Fontenot

4-Dec-02 4:14

Let me also suggest CODBCRecordset. This class encapsulates CRecordset and makes things much more accesiable. IMO that is.

Cheers

***********************
Tony Fontenot
Recreational Solutions
tony@recsolutions.com
***********************

mariox3-Dec-02 22:31

mariox

3-Dec-02 22:31

Dear girls and guys of TheCodeProject

I need to know how can I draw some geometric shapes (GDI or Direct3D) on top of a DirectShow managed, running or paused, multimedia video (AVIs and BMPs), using DirectX 8.1.

Could I get a IDirectDrawVideo and then IDirectDraw (but DirectDraw is deprecated)?

It could be the solution to use overlay filters (although they are more focused on DVD solutions) as IOverlay?

Must I migrate to XP (my platform is W2K) and then use the VMR system?

Thanks in advance.

multiple overlapped I/O - error handling

peterchen3-Dec-02 22:10

CTreeCtrl SetCheck problem

3-Dec-02 22:10

Hi,

I'm sending multiple overlapped I/O requests to a USB device, which it handles dutifully - unless there's an error.

How should I detect that?
I guess I could just send the requests, and then WaitForMultipleObjects to wait for the I/O's to complete. However, I'm not sure what happens when one of the transfers fails - do I have to wait until the remaining transfers time out, etc..

Are there "known good" solution to this scenario?

If I could find a souvenir / just to prove the world was here [sighist]

Brian van der Beek3-Dec-02 21:38

3-Dec-02 21:38

I have a Dialog with a CTreeCtrl that has the TVS_CHECKBOXES style. When I try to initialize the tree control by setting some checkboxes in the OnInitDialog of the dialog the checkboxes are not set. I found out that this is a MFC bug. I haven't been able to find a working workaround for this problem. One thing I did find was setting the image list before calling SetCheck, but this does not seem to work either. Anyone knows a working sollution?

peterchen3-Dec-02 22:05

3-Dec-02 22:05

Clickety[^]

If I could find a souvenir / just to prove the world was here [sighist]

Brian van der Beek3-Dec-02 22:25

3-Dec-02 22:25

Thanks for your reply, but I don't think this article covers my problem. I already tried to modify the style and then set the checkboxes, but still that does not work.

peterchen3-Dec-02 22:45

3-Dec-02 22:45

I thought I already added it...
Can't delve in deeper right now (@ work).

IIRC this one helps:
From InitDialog, Do a Postmessage(WM_APP)
Add a handler for WM_APP, and do the checkbox setting there

(I also have seen I've got to fix the project download Wink | ;)

)

Peter

If I could find a souvenir / just to prove the world was here [sighist]

Brian van der Beek4-Dec-02 1:27

4-Dec-02 1:27

Posting a message in the OnInitDialog does not seem to work either. The message is posted, the SetCheck is called, but still none of the checkboxes is checked.

peterchen4-Dec-02 1:59

4-Dec-02 1:59

Do you use SetitemState to set the check?
i.e.

void TreeCtrl_SetStateImage(CTreeCtrl & tree, HTREEITEM item, int stateImage)
{
  tree.SetItemState(item, INDEXTOSTATEIMAGEMASK(stateImage), TVIS_STATEIMAGEMASK);
}

??
Note: 0 is "no state image", 1 is "unchecked", 2 is "checked" with the default state image list.

If I could find a souvenir / just to prove the world was here [sighist]

Brian van der Beek4-Dec-02 2:25

4-Dec-02 2:25

I tried SetCheck as well as SetItemState and I used 0, 1 and 2 but still it does not work...got any ideas left?

peterchen4-Dec-02 2:36

4-Dec-02 2:36

wow, that's tough...

There's an old version of the article on http://buerger.metropolis.de/bitbucket/howto/checktree.htm, with VC project that works (although there's a small bug in the hit test code, that probably doesn't matter for you)

Another comctl32.dll version (IE update or something) might be a good idea before spending much more time on it.

If I could find a souvenir / just to prove the world was here [sighist]

Brian van der Beek4-Dec-02 2:40

4-Dec-02 2:40

Sorry to bother you again, but the link does not work :

Die angeforderte Seite konnte nicht gefunden werden.

I run windows2000 sp2 and ie 5.5 (that should be sufficient, not?)

peterchen4-Dec-02 2:50