Using OLE DB Consumer Templates
Using OLE DB Consumer Templates
CComBSTR
LoadUDL(const CComBSTR& udlPath)
{
CComPtr<IDataInitialize> spDataInitialize;
HRESULT hr = spDataInitialize.CoCreateInstance( __uuidof(MSDAINITIALIZE));
CComHeapPtr<OLECHAR> conString;
if (SUCCEEDED(hr))
{
hr=spDataInitialize->LoadStringFromStorage(udlPath, &conString);
if(hr!=S_OK)
{
cout<<"LoadStringFromStorage failed"<<endl;
return CComBSTR(L"");
}
return CComBSTR(conString);
}
cout<<"CoCreateInstance( __uuidof(MSDAINITIALIZE)) failed"<<endl;
return CComBSTR(L"");
}
CDataConnection
con;
HRESULT
hr=con.Open(conString);//conString can be generated by LoadUDL function
We can also connect to a database by using CDataSource::Open member function.What
’
s the difference between CDataConnection and CDataSource?
CDataConnection is a useful class for creating clients because it encapsulates necessary objects (data source and session) and some of the work you need to do when connecting to a data source.
//Popup a data link property dialog to connect database
CDataSource source;
HRESULT hr=source.Open();
CComBSTR conStr;
source.GetInitializationString(&conStr,true);
//Popup a data link property dialog to connect database
CDataSource source;
HRESULT hr=source.Open();
CComBSTR conStr;
source.GetInitializationString(&conStr,true);
CComBSTR
GetDatabaseProviderName(const CDataSource& ds)
{
CComVariant var;
HRESULT hr = ds.GetProperty( DBPROPSET_DATASOURCEINFO, DBPROP_PROVIDERNAME, &var );
if(hr==S_OK)
{
return var.bstrVal;
}
return CComBSTR(L"");
}
HRESULT
GetTableNames(const CDataConnection& con,vector<CComBSTR>& names)
{
if(!names.empty())
{
names.clear();
}
CTables ts;
HRESULT hr=ts.Open(con.m_session,NULL,NULL,NULL,_T("TABLE"));
if( FAILED(hr) )
{
cout<<"Unable to open the TABLES schema to get the list of available tables"<<endl;;
return hr;
}
hr = ts.MoveFirst();
while( SUCCEEDED( hr ) && hr != DB_S_ENDOFROWSET )
{
names.push_back(ts.m_szName);
hr = ts.MoveNext();
}
if(names.empty())
{
return S_FALSE;
}
else
{
return S_OK;
}
}
void
GetPrimaryKeys(CDataConnection& con,vector<CString>& pkeys)
{
CPrimaryKeys key;
HRESULT hr=key.Open(con.m_session,NULL,NULL,_T("pet"));
while(S_OK==key.MoveNext())
{
pkeys.push_back(key.m_szColumnName);
}
}
HRESULT
OpenByDynamicAccessor(const CDataConnection& con,const CComBSTR& sql)
{
CCommand<CDynamicAccessor> rs;
CDBPropSet pset( DBPROPSET_ROWSET );
pset.AddProperty( DBPROP_ISequentialStream, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_IStream, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_CANFETCHBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_CANSCROLLBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
return rs.Open(con.m_session, sql, &pset );
}
HRESULT
OpenByDynamicAccessor(CDataConnection& con,const CComBSTR& sql)
{
CCommand<CDynamicAccessor> rs;
CDBPropSet pset( DBPROPSET_ROWSET );
pset.AddProperty( DBPROP_ISequentialStream, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_IStream, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_CANFETCHBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_CANSCROLLBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
//If the table has blob column,you must call this method
rs
.SetBlobHandling( DBBLOBHANDLING_SKIP );
return rs.Open(con.m_session, sql, &pset );
}
Remark-----
Either DBPROP_CLIENTCURSOR or DBPROP_IRowsetScroll property is surpported,the count of columns will be equal to actual count of columns + 1.The column 0 is used for bookmark.
HRESULT
GetColumnInfo(CDataConnection& con,const CComBSTR& sql)
{
CCommand<CDynamicAccessor> rs;
CDBPropSet pset( DBPROPSET_ROWSET );
bool b=pset.AddProperty( DBPROP_ISequentialStream, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_IStream, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_CANFETCHBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_CANSCROLLBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty(DBPROP_IRowsetScroll,true,DBPROPOPTIONS_OPTIONAL);
b=rs.SetBlobHandling( DBBLOBHANDLING_SKIP );
HRESULT hr=rs.Open(con, sql, &pset );
if(hr!=S_OK)
{
return hr;
}
DBTYPE dbtype;
for( DBORDINAL col = 1; col <= rs.GetColumnCount(); col++ )
{
hr=rs.GetColumnType( col, &dbtype );
if( col > 1 )
printf( ", " );
printf( "%S [%d]", rs.GetColumnName( col ), dbtype );
}
DBORDINAL count;
DBCOLUMNINFO* pInfo=NULL;
OLECHAR* pbuffer=NULL;
CComPtr<IColumnsInfo> spColumnsInfo;
rs.m_spRowset->QueryInterface(&spColumnsInfo);
if (SUCCEEDED(hr))
{
hr = spColumnsInfo->GetColumnInfo(&count, &pInfo, &pbuffer);
if(hr!=S_OK)
{
return hr;
}
}
CComPtr<IMalloc> spMalloc;
hr=CoGetMalloc(1,&spMalloc);
spMalloc->Free(pInfo);
spMalloc->Free(pbuffer);
}
HRESULT
GetRowsetSize(CDataConnection& con,const CComBSTR& sql,unsigned long& size)
{
CCommand<CDynamicAccessor> rs;
CDBPropSet pset( DBPROPSET_ROWSET );
bool b=pset.AddProperty( DBPROP_ISequentialStream, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_IStream, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_CANFETCHBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_CANSCROLLBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty(DBPROP_IRowsetScroll,true,DBPROPOPTIONS_OPTIONAL);
b=rs.SetBlobHandling( DBBLOBHANDLING_SKIP );
HRESULT hr=rs.Open(con, sql, &pset );
if(hr!=S_OK)
{
return hr;
}
return rs.GetApproximatePosition(NULL,NULL,&size);
}
HRESULT
ExecuteSQLStatement(CDataConnection& con,const CComBSTR& sql)
{
CCommand<CNoAccessor,CNoRowset> rs;
CDBPropSet pset( DBPROPSET_ROWSET );
return rs.Open(con.m_session, sql, &pset );
}
If we want to make our
db_table attribute class provide the ability of updating its fields’s values,we should pay attention to thus points:
1）Implementing the inner codes
void
GetRowsetProperties(CDBPropSet* pPropSet)
{
pPropSet->AddProperty(DBPROP_CANFETCHBACKWARDS, true, DBPROPOPTIONS_OPTIONAL);
pPropSet->AddProperty(DBPROP_CANSCROLLBACKWARDS, true, DBPROPOPTIONS_OPTIONAL);
pPropSet->AddProperty(DBPROP_IRowsetUpdate,true,DBPROPOPTIONS_OPTIONAL);
pPropSet->AddProperty(DBPROP_IRowsetChange, true, DBPROPOPTIONS_OPTIONAL);
pPropSet->AddProperty(DBPROP_UPDATABILITY, DBPROPVAL_UP_CHANGE);
}
2）The codes of client
#include
"stdafx.h"
#include
"sender.h"
int
_tmain(int argc, _TCHAR* argv[])
{
::CoInitialize(NULL);
Csender s;
s.OpenAll();
HRESULT hr=s.MoveFirst();
s.m_com_num=11;
s.SetData();
hr=s.UpdateAll();
::CoUninitialize();
return 0;
}
SetData() member function must be called.
Please refer to the below url:
CTable_1
table;
HRESULT
hr=table.OpenAll();
hr
=table.MoveFirst();
table
.m_a=5;
table
.m_dwaStatus=DBSTATUS_S_OK;
table
.m_dwaLength=4;
hr
=table.Insert();
Please refer to the below url:
Please see the arctile of MSDN named as Using Multiple Accessors on a Rowset
Definition----
A saved placeholder value that identifies a row in a rowset and can later be used by the consumer to retrieve that particular row.
void
GetBookMark(CDataConnection& con,const CComBSTR& sql)
{
CCommand<CDynamicAccessor> rs;
CDBPropSet pset( DBPROPSET_ROWSET );
pset.AddProperty( DBPROP_ISequentialStream, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_IStream, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_CANFETCHBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_CANSCROLLBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
bool b=pset.AddProperty(DBPROP_CLIENTCURSOR,true,DBPROPOPTIONS_REQUIRED);
rs.SetBlobHandling( DBBLOBHANDLING_SKIP );
HRESULT hr=rs.Open(con.m_session, sql, &pset );
DBORDINAL count=rs.GetColumnCount();
CBookmark<> firstmark;
rs.MoveFirst();
char* pV=static_cast<char*>(rs.GetValue(1));
hr=rs.GetBookmark(&firstmark);
while(S_OK==rs.MoveNext())
{
CBookmark<> bookmark;
hr=rs.GetBookmark(&bookmark);
BYTE* p=bookmark.GetBuffer();
}
hr=rs.MoveToBookmark(firstmark);
pV=static_cast<char*>(rs.GetValue(1));
}
The bookmark retrieved through upon codes is numeric bookmark,the value is equalt to the index of current row.We can also use SetBookmark memeber function set the current bookmark
’
s value.
void
GetXMLData(CDataConnection& con,const CComBSTR& sql)
{
CCommand<CXMLAccessor> rs;
CDBPropSet pset( DBPROPSET_ROWSET );
HRESULT hr=rs.Open(con.m_session, sql, &pset );
CStringW str;
while(S_OK==rs.MoveNext())
{
rs.GetXMLRowData(str,true);
}
}
void
ConnectDatabase(LPTSTR conString)
{
CComBSTR str(L"Provider=MSDASQL.1;Persist Security Info=True;");
str+=conString;
CDataConnection con;
HRESULT hr=con.Open(str);
if(hr!=S_OK)
{
CDBErrorInfo info;
LCID lcid = ::GetUserDefaultLCID();
ULONG records;
hr=info.GetErrorRecords(con.m_source.m_spInit,__uuidof(IDBInitialize),&records);
CComBSTR errorMsg,source;
hr=info.GetAllErrorInfo(0,lcid,&errorMsg,&source);
string s("Failed connect to database: ");
s+=CW2A(errorMsg.m_str);
throw CTXDatabaseExcep(hr,s);
}
}
void
ThrowDBException(const string& context)
{
CDBErrorInfo info;
LCID lcid = ::GetUserDefaultLCID();
ULONG records;
HRESULT hr=info.GetErrorRecords(m_con.m_source.m_spInit,__uuidof(IDBInitialize),&records);
if(hr!=S_OK)
{
throw std::runtime_error("CDBErrorInfo::GetErrorRecords faield");
}
CComBSTR errorMsg,source;
hr=info.GetAllErrorInfo(0,lcid,&errorMsg,&source);
if(hr!=S_OK)
{
throw std::runtime_error("CDBErrorInfo::GetAllErrorInfo faield");
}
string s=context+" : ";
s+=CW2A(errorMsg.m_str);
throw std::exception(s.c_str());
}
How can I use native client?Just setting the udl property,and using native client provider.
When I fetch 10,000 records ,and each record has 118 columns,Native Client provider is faster than OLE DB provider.That’s my test function.
DWORD
PerformanceTest(CDataConnection& con,const CComBSTR& sql)
{
DWORD x=GetTickCount();
CCommand<CDynamicAccessor> rs;
CDBPropSet pset( DBPROPSET_ROWSET );
pset.AddProperty( DBPROP_ISequentialStream, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_IStream, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_CANFETCHBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
pset.AddProperty( DBPROP_CANSCROLLBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
bool b=pset.AddProperty(DBPROP_CLIENTCURSOR,true,DBPROPOPTIONS_REQUIRED);
rs.SetBlobHandling( DBBLOBHANDLING_SKIP );
rs.Open(con.m_session, sql, &pset );
while(S_OK==rs.MoveNext())
{}
return GetTickCount()-x;
}
OLE DB provider always spend 2,000 million seconds at least,and Native Client always spend less than 1,790 million seconds.
CREATE PROCEDURE test AS
delete from carInfo2
GO
HRESULT
CallStoredProcedureNoParameterNoResult(CDataConnection& con,const CComBSTR& procName)
{
CCommand<CDynamicAccessor> rs;
CDBPropSet pset;
return rs.Open(con.m_session, procName, &pset );
}
CREATE PROCEDURE test2AS
select * from carInfo2
GO
HRESULT
CallStoredProcedureNoParameter(CDataConnection& con,const CComBSTR& procName)
{
CCommand<CDynamicAccessor> rs;
CDBPropSet pset( DBPROPSET_ROWSET );
bool b=pset.AddProperty( DBPROP_ISequentialStream, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_IStream, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_CANFETCHBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_CANSCROLLBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty(DBPROP_IRowsetScroll,true,DBPROPOPTIONS_OPTIONAL);
b=pset.AddProperty(DBPROP_CLIENTCURSOR,true,DBPROPOPTIONS_OPTIONAL);
HRESULT hr=rs.Open(con.m_session, procName, &pset );
if(S_OK==hr)
{
DBCOUNTITEM count(0);
hr=rs.GetApproximatePosition(0,0,&count);
return hr;
}
else
{
return hr;
}
}
CREATE PROCEDURE test3 @id int
AS
delete from carInfo2
where carID=@id
GO
HRESULT
CallStoredProcedureNoRowset(CDataConnection& con,const int parameter)
{
CCommand<CDynamicParameterAccessor,CNoRowset> rs;
HRESULT hr = rs.Create(con.m_session,"exec test3 ?");
hr=rs.Prepare();
void* p;
rs.BindParameters(&rs.m_hParameterAccessor,rs.m_spCommand,&p);
bool r=rs.SetParam<int>(1,¶meter);
return rs.Open(NULL,NULL,0);
}
CREATE PROCEDURE test4 @id int
as
select * from carInfo2
select * from carInfo2
where carID=@id
GO
HRESULT
CallStoredProcedure(CDataConnection& con,const int parameter)
{
CCommand<CDynamicParameterAccessor,CRowset> rs;
HRESULT hr = rs.Create(con.m_session,"exec test4 ?");
hr=rs.Prepare();
void* p;
rs.BindParameters(&rs.m_hParameterAccessor,rs.m_spCommand,&p);
bool r=rs.SetParam<int>(1,¶meter);
CDBPropSet pset( DBPROPSET_ROWSET );
bool b=pset.AddProperty( DBPROP_ISequentialStream, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_IStream, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_CANFETCHBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty( DBPROP_CANSCROLLBACKWARDS, true, DBPROPOPTIONS_OPTIONAL );
b=pset.AddProperty(DBPROP_IRowsetScroll,true,DBPROPOPTIONS_OPTIONAL);
b=pset.AddProperty(DBPROP_IRowsetUpdate,true,DBPROPOPTIONS_OPTIONAL);
b=pset.AddProperty(DBPROP_IRowsetChange, true, DBPROPOPTIONS_OPTIONAL);
hr=rs.Open(&pset);
hr=rs.MoveFirst();
DBORDINAL l=1;
int* pv=(int*)rs.GetValue(l);
return hr;
}