Re: RecordsetPtr & Command's Execute() method
From: Val Mazur (group51a_at_hotmail.com)
Date: 02/28/04
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Date: Sat, 28 Feb 2004 13:28:38 -0500
Hi Chris,
It is exact same as a another type of the recordset, but just has some
limitations. I am not a C++ guy, but I will try to describe some limitations
and usage.
First if all, when you open read-only, forward-only recordset, you need to
check EOF property to see if recordset has anything. In VB it looks like
Set MyRecordset=MyCommand.Execute "SELECT ...."
If Not .EOF Then
'Do some staff here
end if
Since you cannot get record count, you need to use EOF property of the
recordset to check if you have any records. Now you can navigate recordset,
but here you have some limitations. First you can use only MoveFirst,
MoveNext, MoveLast methods, not MovePrevious. In case of MoveNext and
MoveLast, provider just scrolls recordset to the next or to the last record.
In case of MoveFirst, provider re-opens recordset again. It happens because
virtually you cannot move back and provider has to open cursor again. This
is basically main difference between forward-only and other types of the
recordset. If you have any specific questions, then you could post them here
-- Val Mazur Microsoft MVP "Chris Martin" <nospam@please11111.net> wrote in message news:lEA%b.130741$jk2.545383@attbi_s53... > Thanks for the reply. I guess my real problem is I don't know how to use > this a read-only, forward-only Recordset. If anyone could provide some > sample code or an MSDN article, that'd be great. > > Thanks, > C. Martin > > "Val Mazur" <group51a@hotmail.com> wrote in message > news:OTPXBVO$DHA.2516@TK2MSFTNGP11.phx.gbl... >> Hi Chris, >> >> Do you want to say that you do not like recordcount -1? If yes, then it >> is >> expected result in your case, because recordset is read-only, >> forward-only >> and provider is not capable to return actual record count in this case, > but >> recordset is opened and you could use it. Check next KB for more > information >> >> http://support.microsoft.com/default.aspx?scid=kb;en-us;194973 >> >> -- >> Val Mazur >> Microsoft MVP >> >> "Chris Martin" <nospam@please11111.net> wrote in message >> news:o_x%b.130127$jk2.542397@attbi_s53... >> >I am trying to get back data from a "SELECT" query, and am having >> >trouble >> > doing anything with the RecordsetPtr returned from a Command's >> > Execute() >> > method. The docs say: >> > >> >> The returned Recordset object is always a read-only, forward-only > cursor. >> > >> > Am I doing something incorrect in accessing the data from this > Recordset? >> > I >> > have gotten SELECT queries to work using Recordset's Open() method, but > I >> > wanted to use the Command's Execute() instead. >> > >> > If there is a good reason for using a different method, please explain. >> > >> > /* code simplified for brevity */ >> > _ConnectionPtr m_pConnection; >> > _CommandPtr m_pCommand; >> > _RecordsetPtr pRs; >> > >> > m_pConnection.CreateInstance(__uuidof(Connection)); >> > m_pCommand.CreateInstance(__uuidof(Command)); >> > >> > m_pConnection->Open(m_strConn, lpstrUserID, lpstrPword, NULL); >> > >> > m_pCommand->ActiveConnection = m_pConnection; >> > m_pCommand->CommandText = "SELECT * FROM Customers"; >> > >> > pRs = m_pCommand->Execute(NULL, NULL, adCmdText); >> > >> > long count = pRs->GetRecordCount(); // returns -1 >> > _bstr_t str = pRs->GetString(adClipString, 1, ",", "\n", ""); // >> > returns >> > garbage >> > /* end */ >> > >> > TIA, >> > C. Martin >> > >> > >> >> > >
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