C++使用OLEDB连接SQL Server

Windows环境中使用OLEDB连接SQL Server，本文只作为对前两篇博文的补充，并非推荐做法。

下面例子依次调用了：

• 初始化环境
• 连接SQL Server
• 执行查询
• 关闭连接

示例代码：
oledbTest.cpp

#include "stdafx.h"
#include <windows.h>
#include <sys\timeb.h>
#include <time.h>
#include <stdio.h>
#include <iostream>
#include <map>
#include <atldbcli.h>
#include <atlconv.h>
using namespace std;

typedef struct result
{
    char ename[19];
    char cname[100];
    DBSTATUS dwEnameStatus;
    DBSTATUS dwCnameStatus;
} RESULT;

int _tmain(int argc, _TCHAR* argv[])
{
    HRESULT hr;
    CDataSource  m_ds;
    CSession m_session;

    //连接串指定数据库，用户名，密码
    char szConnectionString[512] = "Provider=SQLNCLI10.1;Data Source=10.2.0.10;Initial Catalog=MYDB;User ID=user;Password=passwd;Application Name=SQLSERVER;MARS Connection=True";

    ::CoInitialize(NULL);

    //连接数据库
    hr = m_ds.OpenFromInitializationString(CA2W(szConnectionString));

    //打开会话
    hr = m_session.Open(m_ds);

    DBORDINAL ulColumns = 0;
    CDBPropSet dbPropSet(DBPROPSET_ROWSET);
    CCommand<CManualAccessor, CRowset, CNoMultipleResults> m_command;
    hr = m_command.CreateCommand(m_session);

    CComPtr<ICommandText> spCommandText;
    hr = m_command.m_spCommand->QueryInterface(&spCommandText);
    USES_CONVERSION;

    //查询语句
    const TCHAR *cmd = _T(" select col1, col2 from table1 ");

    hr = spCommandText->SetCommandText(DBGUID_SQL, T2COLE(cmd));

    dbPropSet.AddProperty(DBPROP_ISequentialStream, true);

    hr = m_command.Open(&dbPropSet, NULL, false);

    DBCOLUMNINFO *m_pColumnInfo;
    LPOLESTR m_pStrings;

    //获取列信息
    hr = m_command.GetColumnInfo(&ulColumns
        , &m_pColumnInfo
        , &m_pStrings);

    BYTE * m_pRowInfoBuff;

    //初始化列绑定字段
    DBCOUNTITEM cbRowSize = (m_pColumnInfo[0].ulColumnSize + 1) * sizeof(CHAR);
    DBCOUNTITEM cbRowSize2 = (m_pColumnInfo[1].ulColumnSize + 1) * sizeof(CHAR);

    RESULT rst;

    int bufferSize = sizeof(rst.ename) + sizeof(rst.cname) +1;
    m_pRowInfoBuff = new BYTE[bufferSize];

    hr = m_command.CreateAccessor(ulColumns, m_pRowInfoBuff, (DBLENGTH)bufferSize);

    //DBORDINAL* pLength = (DBORDINAL*)(m_pRowInfoBuff + cbRowSize);
    //DBSTATUS* pStatus = (DBSTATUS*)(m_pRowInfoBuff + cbRowSize);
    DBTYPE dbType=DBTYPE_STR;
    DBLENGTH dbLength =  (m_pColumnInfo[0].ulColumnSize + 1) * sizeof(TCHAR);
    DBLENGTH dbLength2 =  (m_pColumnInfo[1].ulColumnSize + 1) * sizeof(TCHAR);

    //m_command.AddBindEntry(1, dbType, dbLength, pValue, pLength, pStatus);
    m_command.AddBindEntry(1, dbType, dbLength, rst.ename, NULL, &rst.dwEnameStatus);
    m_command.AddBindEntry(2, dbType, dbLength2, rst.cname, NULL, &rst.dwCnameStatus);

    hr = m_command.Bind();

    //获取查询信息
    while(S_OK == m_command.MoveNext())
    {
        printf(" ename = [%s] ,cname = [%s]\n", rst.ename, rst.cname);
    }

    //关闭连接
    m_command.Close();
    m_session.Close();
    m_ds.Close();

    ::CoUninitialize();

    ::getchar();

}