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CDaoQuerydef and CDaoRecordset; running a query help

Posted on 1998-08-26
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Last Modified: 2013-11-19
I'm trying to do a simple search through my database.  I created a query in Access called "Simple Search".  The Criteria is: [Title] like [Search String].  Title is a field in the database.  Search String is a parameter that is set by my program.  This is my code:


//m_pDaoWorkspace and m_pDaoDatabase have already been created

CDaoQueryDef q(m_pDaoDatabase);
q.Open("Simple Search");
int isRet = q.GetReturnsRecords(); // this returns 1
int param = q.GetParameterCount(); // this returns 1
CDaoParameterInfo info;
q.GetParameterInfo(0,info);  // the 1 param = Search String

q.SetParamValue("Search String",COleVariant("*Uranium*"));
//I hope I have done this right.This might explain problem

CMyRecordset *r; // derived from CDaoRecordset
r = new CMyRecordset( m_pDaoDatabase );

if( ! r->IsOpen( ))
{
   try
   {
      r->Open(&q);
   }
   catch( CDaoException* eDaoException )
   {
      eDaoException->Delete( );
      return FALSE;
   }
}
int recs = r->GetRecordCount();

This last line is the problem.  it returns 0.


If I do not pass the CQueryDef pointer to the Open function of CMyRecordset and just open it as a normal dynset recordset GetRecordCount returns 220 as it should.  There are 220 records in the database.  So the problem lies in my CQueryDef usage and most likely, I figure how I set the parameter.  Because if I run the query in MS-Access with the same value as I set it in my program it returns some 50 records.

I'd really appreciate any information I could get about things to look at.
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Question by:LukeSkywalker
2 Comments
 
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Accepted Solution

by:
milenvk earned 200 total points
ID: 1321329
Yes the problem is where you suppose it is. DAO uses ANSI character strings, but COleVariant converts your "*Uranium*" parameter to BSTR (i.e. wide character string). Here's what you should do to fix the problem. Replace the line:

q.SetParamValue("Search String",COleVariant("*Uranium*"));

with

q.SetParamValue("Search String",COleVariant("*Uranium*", VT_BSTRT));

See VT_BSTRT is the BSTR type that uses ANSI convension. VT_BSTR is the one that's using the wide character convension and it is set by the COleVariant contrustor by default.

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Author Comment

by:LukeSkywalker
ID: 1321330
You suggestion worked to solve that problem.  Thank you!
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