VC++ 訪问数据库实例具体解释图解

一 ADO 方式訪问 Access

新建一个对话框project，加入控件，如图；

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创建Access数据库如图；

应用程序启动时进行COM初始化。

BOOL CDemoApp::InitInstance()

{

if (!SUCCEEDED(CoInitialize(NULL)))

{

::AfxMessageBox(_T("Failed to initialize COM!"));

return FALSE;

}



AfxEnableControlContainer();

对话框类实现文件代码例如以下；

// DemoDlg.cpp : implementation file

// Download by http://www.NewXing.com





#include "stdafx.h"

#include "Demo.h"

#include "DemoDlg.h"





#ifdef _DEBUG

#define new DEBUG_NEW

#undef THIS_FILE

static char THIS_FILE[] = __FILE__;

#endif





/////////////////////////////////////////////////////////////////////////////

// CAboutDlg dialog used for App About





class CAboutDlg : public CDialog

{

public:

CAboutDlg();





// Dialog Data

//{{AFX_DATA(CAboutDlg)

enum { IDD = IDD_ABOUTBOX };

//}}AFX_DATA





// ClassWizard generated virtual function overrides

//{{AFX_VIRTUAL(CAboutDlg)

protected:

virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support

//}}AFX_VIRTUAL





// Implementation

protected:

//{{AFX_MSG(CAboutDlg)

//}}AFX_MSG

DECLARE_MESSAGE_MAP()

};





CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)

{

//{{AFX_DATA_INIT(CAboutDlg)

//}}AFX_DATA_INIT

}





void CAboutDlg::DoDataExchange(CDataExchange* pDX)

{

CDialog::DoDataExchange(pDX);

//{{AFX_DATA_MAP(CAboutDlg)

//}}AFX_DATA_MAP

}





BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)

//{{AFX_MSG_MAP(CAboutDlg)

// No message handlers

//}}AFX_MSG_MAP

END_MESSAGE_MAP()





/////////////////////////////////////////////////////////////////////////////

// CDemoDlg dialog





CDemoDlg::CDemoDlg(CWnd* pParent /*=NULL*/)

: CDialog(CDemoDlg::IDD, pParent)

{

//{{AFX_DATA_INIT(CDemoDlg)

//}}AFX_DATA_INIT

// Note that LoadIcon does not require a subsequent DestroyIcon in Win32

m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);





if (!SUCCEEDED(m_pConnection.CreateInstance(__uuidof(Connection))))

{

m_pConnection = NULL;

TRACE(_T("Database CreateInstance failed"));

}





if (!SUCCEEDED(m_pRecordset.CreateInstance(__uuidof(Recordset))))

{

m_pRecordset = NULL;

TRACE(_T("Recordset CreateInstance Failed!"));

}





//打开数据库

CString strConnect = _T("Provider=Microsoft.Jet.OLEDB.4.0;Data Source= Demo.mdb");

if (!OpenDatabase(strConnect))

{

AfxMessageBox(_T("数据库打开失败。

"));

return;

}



//打开记录集

if (!OpenRecordset(_T("SELECT * FROM DemoTable")))

{

AfxMessageBox(_T("记录集打开失败。"));

return;

}

}





CDemoDlg::~CDemoDlg()

{

m_pRecordset->Close();

m_pConnection->Close();

}





void CDemoDlg::DoDataExchange(CDataExchange* pDX)

{

CDialog::DoDataExchange(pDX);

//{{AFX_DATA_MAP(CDemoDlg)

//}}AFX_DATA_MAP

}





BEGIN_MESSAGE_MAP(CDemoDlg, CDialog)

//{{AFX_MSG_MAP(CDemoDlg)

ON_WM_SYSCOMMAND()

ON_WM_PAINT()

ON_WM_QUERYDRAGICON()

ON_BN_CLICKED(IDC_FIND, OnFind)

//}}AFX_MSG_MAP

END_MESSAGE_MAP()





/////////////////////////////////////////////////////////////////////////////

// CDemoDlg message handlers





BOOL CDemoDlg::OnInitDialog()

{

CDialog::OnInitDialog();





// Add "About..." menu item to system menu.





// IDM_ABOUTBOX must be in the system command range.

ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);

ASSERT(IDM_ABOUTBOX < 0xF000);





CMenu* pSysMenu = GetSystemMenu(FALSE);

if (pSysMenu != NULL)

{

CString strAboutMenu;

strAboutMenu.LoadString(IDS_ABOUTBOX);

if (!strAboutMenu.IsEmpty())

{

pSysMenu->AppendMenu(MF_SEPARATOR);

pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);

}

}





// Set the icon for this dialog.  The framework does this automatically

//  when the application's main window is not a dialog

SetIcon(m_hIcon, TRUE);// Set big icon

SetIcon(m_hIcon, FALSE);// Set small icon





//初始化ListCtrl

CListCtrl* pListCtrl = (CListCtrl*)GetDlgItem(IDC_LIST);

pListCtrl->SetExtendedStyle(LVS_EX_FULLROWSELECT | LVS_EX_GRIDLINES);

pListCtrl->InsertColumn(1, _T("序号"), LVCFMT_CENTER, 80);

pListCtrl->InsertColumn(2, _T("姓名"), LVCFMT_CENTER, 100);

pListCtrl->InsertColumn(3, _T("年龄"), LVCFMT_CENTER, 100);





return TRUE;

}





void CDemoDlg::OnSysCommand(UINT nID, LPARAM lParam)

{

if ((nID & 0xFFF0) == IDM_ABOUTBOX)

{

CAboutDlg dlgAbout;

dlgAbout.DoModal();

}

else

{

CDialog::OnSysCommand(nID, lParam);

}

}





// If you add a minimize button to your dialog, you will need the code below

//  to draw the icon.  For MFC applications using the document/view model,

//  this is automatically done for you by the framework.





void CDemoDlg::OnPaint() 

{

if (IsIconic())

{

CPaintDC dc(this); // device context for painting





SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);





// Center icon in client rectangle

int cxIcon = GetSystemMetrics(SM_CXICON);

int cyIcon = GetSystemMetrics(SM_CYICON);

CRect rect;

GetClientRect(&rect);

int x = (rect.Width() - cxIcon + 1) / 2;

int y = (rect.Height() - cyIcon + 1) / 2;





// Draw the icon

dc.DrawIcon(x, y, m_hIcon);

}

else

{

CDialog::OnPaint();

}

}





// The system calls this to obtain the cursor to display while the user drags

//  the minimized window.

HCURSOR CDemoDlg::OnQueryDragIcon()

{

return (HCURSOR) m_hIcon;

}





BOOL CDemoDlg::OpenDatabase(LPCTSTR lpszConnect, long nOptions)

{

ASSERT(m_pConnection != NULL);

ASSERT(lpszConnect != NULL);

ASSERT(AfxIsValidString(lpszConnect));



//打开数据库连接

try

{

return SUCCEEDED(m_pConnection->Open(_bstr_t(lpszConnect), 

_T(""), _T(""), nOptions));

}

catch (_com_error& e)

{

TRACE(_T("%s\n"), e.ErrorMessage());

return FALSE;

}

}





BOOL CDemoDlg::CloseDatabase()

{

ASSERT(m_pConnection != NULL);





//关闭数据库连接

try

{

if (m_pConnection->State & adStateOpen) 

{

return SUCCEEDED(m_pConnection->Close());

}

else

{

return TRUE;

}

}

catch (_com_error& e)

{

TRACE(_T("%s\n"), e.ErrorMessage());

return FALSE;

} 

}





BOOL CDemoDlg::OpenRecordset(LPCTSTR lpszSource, long nCursorType, long nLockType, long nOptions)

{

ASSERT(m_pConnection != NULL);

ASSERT(m_pRecordset != NULL);

ASSERT(lpszSource != NULL);

ASSERT(AfxIsValidString(lpszSource));





//打开记录集

try

{

return (SUCCEEDED(m_pRecordset->Open(_variant_t(lpszSource),

m_pConnection.GetInterfacePtr(),

(CursorTypeEnum)nCursorType, 

(LockTypeEnum)nLockType,

nOptions)));

}

catch(_com_error e)

{

TRACE(_T("%s\n"), e.ErrorMessage());

return FALSE;

}

}





BOOL CDemoDlg::CloseRecorset()

{

ASSERT(m_pRecordset != NULL);





//关闭记录集

try

{

if (m_pRecordset->State & adStateOpen) 

{

return SUCCEEDED(m_pRecordset->Close());

}

else

{

return TRUE;

}

}

catch (_com_error e)

{

TRACE(_T("%s\n"), e.ErrorMessage());

return FALSE;

}

}





void CDemoDlg::OnFind() 

{

if (!(m_pRecordset->State & adStateOpen))

{

AfxMessageBox((_T("记录集未打开。

")));

return;

}





//查找条件

CString strCriteria = _T("");

CString strName = _T("");

GetDlgItemText(IDC_NAME, strName);

strCriteria.Format(_T("NAME like '%s'"), strName);





//查找记录集

CListCtrl* pListCtrl = (CListCtrl*)GetDlgItem(IDC_LIST);

pListCtrl->DeleteAllItems();

if (m_pRecordset->BOF && m_pRecordset->adoEOF)

{

return;

}

m_pRecordset->MoveFirst();

int n = 0;

m_pRecordset->Find(_bstr_t(strCriteria), 0, adSearchForward);

while (!m_pRecordset->adoEOF)

{

_variant_t varValue;

CString strName = _T("");

int nAge = 0;





varValue = m_pRecordset->GetCollect(_variant_t(_T("NAME")));

if (varValue.vt != VT_NULL)

{

strName = varValue.bstrVal;

}

else

{

strName = _T("");

}





varValue = m_pRecordset->GetCollect(_variant_t(_T("AGE")));

if (varValue.vt != VT_NULL)

{

nAge = varValue.intVal;

}

else

{

nAge = 0;

}





//刷新ListCtrl

CString strText = _T("");

strText.Format(_T("%d"), n + 1);

pListCtrl->InsertItem(n, strText);

strText.Format(_T("%s"), strName);

pListCtrl->SetItemText(n, 1, strText);

strText.Format(_T("%d"), nAge);

pListCtrl->SetItemText(n, 2, strText);

n++;





m_pRecordset->Find(_bstr_t(strCriteria), 1, adSearchForward);

}

}

折叠起来看下函数。

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代码就不解释了；函数含义比較明白。除了操作数据库。ADO方式还有COM相关操作。

效果：

VC在调试时。Data Source= Demo.mdb。这种语句，訪问的不是Debug文件夹下的Demo.mdb，是和Debug文件夹同级；

假设Debug文件夹同级没有数据库，则打开数据库失败。

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project下载

http://pan.baidu.com/s/1slEEOMD

Access工具下载

http://blog.csdn.net/bcbobo21cn/article/details/51000041

VC6下载

http://blog.csdn.net/bcbobo21cn/article/details/44200205

二 VC 訪问 sqlite3

首先用sqlite3创建一个数据库，设备db。

创建表并插入数据；

接下来在VC6中新建一个控制台project。

代码。

#include <stdio.h> 

#include <stdlib.h> 

#include <sqlite3.h> 

int column_names_printed = 0; 

void print_row(int n_values, char** values) 

{ 

    int i; 

    for (i = 0; i < n_values; ++i) { 

        printf("%10s", values[i]); 

    } 

    printf("\n"); 

} 

int print_result(void* data, int n_columns, char** column_values, char** column_names) 

{ 

    if (!column_names_printed) { 

        print_row(n_columns, column_names); 

        column_names_printed = 1; 

    } 

    

    print_row(n_columns, column_values); 

   

   return 0; 

} 

int main() 

{ 

    sqlite3 *db=NULL; 

    char *errMsg = NULL; 

    int rc; 

    

    rc = sqlite3_open("shebei.db", &db); 

    if( rc ){ 

        fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db)); 

        sqlite3_close(db); 

        exit(1); 

    } 

    else printf("open shebei.db successfully!\n"); 

    

    column_names_printed = 0; 

    rc = sqlite3_exec(db, "SELECT shebei.* FROM shebei;", print_result, NULL, &errMsg); 

    column_names_printed = 1; 

    printf("\n"); 

    

    printf("error code: %d\n", rc); 

    printf("error message: %s\n", errMsg); 

    sqlite3_close(db); 

    return 0; 

}

注意假设例如以下的换行语句。

rc = sqlite3_exec(db, "CREATE TABLE students(number varchar(10), name varchar(10), \ 

                           sex varchar(6), age varchar(2));", NULL, NULL, NULL);

\之后假设有空格；则会出现；

Y:\dddd20\sqlitedemo1\demo1.cpp(39) : warning C4129: ' ' : unrecognized character escape sequence

删除空格就可以；

如今我们有sqlite3.dll跟一个sqlite3.def文件，并没实用于VC++6.0的lib文件，能够利用sqlite3.def文件生成，过程例如以下： 

  1.将sqlite3.h（D:\sqlite-amalgamation-3_6_23.zip）复制到C:\Program Files\Microsoft Visual Studio\VC98\Include文件夹下，这时编译可通过，但链接错误，由于没有LIB文件（） 

  2.启动一个命令行程序，进入VC的安装文件夹C:\Program Files\Microsoft Visual Studio\VC98\Bin，在这个文件夹以下有一个LIB.exe文件，使用它就能生成sqlite3.lib文件，将sqlite3.def文件放到同样文件夹，或者绝对路径也能够。 然后在命令行输入例如以下命令： 

   LIB /MACHINE:IX86 /DEF:sqlite3.def 

  该命令生成两个文件：sqlite3.lib和sqlite3.exp 

   执行该命令时。假设提示找不到MSPDB60.DLL文件，可从其他文件夹拷贝至Bin文件夹下 

  3.将生成的sqlite3.lib复制到Lib文件夹下,将sqlite3.dll复制到C:\WINNT\system32文件夹下 

   4.将sqlite3.lib增加到project链接中，Project->Settings,Link选项卡，Object/library modules最后添入sqlite3.lib

參阅：http://mxdxm.iteye.com/blog/634772

操作过程和完毕结果例如以下图；

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把环境配置好；编译执行程序。效果例如以下；

project下载

sqlite相关下载。包含，h、Lib、dll文件;

http://pan.baidu.com/s/1slEEOMD

三 ADO訪问数据库出现C2146、C2501

demodlg.h(25) : error C2146: syntax error : missing ';' before identifier 'm_pConnection'

demodlg.h(25) : error C2501: '_ConnectionPtr' : missing storage-class or type specifiers

demodlg.h(25) : error C2501: 'm_pConnection' : missing storage-class or type specifiers



在stdafx.h中增加例如以下语句再构建；



#import "c:\Program Files (x86)\common files\system\ado\msado15.dll"\

no_namespace\

rename("EOF", "adoEOF")

另外再看是否少了}；