ODBC MFC: can't use SELECT properly

Question

0.00/5 (No votes)

See more:

Hi!

I'm trying to use ODBC with an Access 2000 database in a C++ MFC application.

I use the following code to SELECT an entry (which exists) in my Database:

C++

CNoeud myNode;
myNode.Open(CRecordset::dynaset, L"SELECT * FROM Noeuds where Identifiant_Noeud=5", CRecordset::none);

AfxMessageBox(L"myNode: " + myNode.m_Identifiant_Noeud);

myNode.Close();

Note:
- Identifiant_Noeud is the primary key.
- I don't open nor close the database, I only use the CNoeud object Open() and Close() methods.

But the AfxMessageBox only shows "e:" (I don't know why !).

I'm new to all this, could you explain me how to do my simple SELECT statement? I'm probably missing something obvious...
Thanks!

What I have tried:

If I wrote the following:

CNoeud myNode;

myNode.Open(CRecordset::dynaset, L"SELECT * FROM Noeuds where Identifiant_Noeud=5", CRecordset::none);

if (myNode.IsEOF()) AfxMessageBox(L"no entry");
myNode.Close();

No message box is shown, so I suppose the CNoeud object is not empty.

Posted 13-Dec-17 0:49am

SheepSpeech

Updated 13-Dec-17 1:26am

v2

Add a Solution

Comments

W∴ Balboos, GHB 13-Dec-17 7:12am

Connection String?

At least from what you sent, you've no connection to the database.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Jochen Arndt · Accepted Answer · 2017-12-13T01:26:00

Solution 1

The keyword is C/C++ pointer arithmetic.

The first parameter of the AfxMessageBox() function is an LPCTSTR string pointer. You are passing the address of a constant string and adds the value "5" (myNode.m_Identifiant_Noeud is as primary key probably some kind of int). So the message box shows the string starting at the 6th character (zero based 5th).

You can't concatenate strings with the + operator in C/C++.

You have to create a formatted string and show that:

C++

CString strMsg;
strMsg.Format(_T("myNode: %d"), myNode.m_Identifiant_Noeud);
AfxMessageBox(strMsg.GetString());

Posted 13-Dec-17 1:26am

Jochen Arndt

Comments

SheepSpeech 13-Dec-17 9:19am

Thanks !
I just finished a project in C#, my mistake. But I saw this on the internet and it seems to work, I use it for my databases exceptions: AfxMessageBox(L"Database error: " + e->m_strError);

Jochen Arndt 13-Dec-17 9:30am

There m_strError is a CString. That supports concatening strings with the + operator (but not other types like int). The above will create a temporary CString (because one operand is a CString) which is then passed using the implicit PCXSTR() operator.

Thank you for accepting my solution.