C++对数据库的操作有多种方式,这里笔者抛砖引玉,以ADO存取Access数据库的例子来说明在C++是如何进行数据库编程的。
ADO操纵数据库主要用到三个智能指针:
_ConnectionPtr: 用于连接数据库
_RecordsetPtr: 用于操纵结果集
_CommandPtr: 用于执行SQL命令
下面用一个完整的例子来说明如何使用这三个智能指针。
首先建立一个Access数据库,名字为testdb.mdb,里面只有一个表txl,表里面有3个字段:
ID : 自动增长
Name: text类型,长度50
QQ: text类型, 长度50
下面是完整的C++代码,实现了添加、删除、查询和更新的操作:
/* txl.cpp */
#include
#include
// 导入ADO组件,它包含了三个操纵数据库的智能指针
#import "c:\program files\common files\system\\ado\\msado15.dll" \
no_namespace rename ("EOF", "adoEOF")
using namespace std;
void DisplayMenu();
BOOL DisplayAllRecord();
BOOL AddRecord();
BOOL DeleteRecord();
BOOL UpdateRecord();
void SearchRecord();
// 操纵数据库的三个智能指针
_ConnectionPtr g_pConnection;
_RecordsetPtr g_pRecordset;
_CommandPtr g_pCommand;
int main()
{
int n_Choice;
CoInitialize(NULL); // Initialize Com
// Create and Open Connection
g_pConnection.CreateInstance(__uuidof(Connection));
// SQL Command Executing Time
g_pConnection->put_CommandTimeout(long(5));
try
{
// Open Connection
g_pConnection->Open("Provider=Microsoft.Jet.OLEDB.4.0; Data Source=testdb.mdb", "", "", adModeUnknown);
}
catch(_com_error e)
{
cout << "Database connection failed :" << e.ErrorMessage() << endl;
return -1;
}
g_pRecordset.CreateInstance(__uuidof(Recordset));
g_pCommand.CreateInstance(__uuidof(Command));
g_pCommand->ActiveConnection = g_pConnection;
DisplayMenu();
cin >> n_Choice;
while ( n_Choice )
{
switch ( n_Choice )
{
case 1:
//DisplayMenu();
break;
case 2:
DisplayAllRecord();
break;
case 3:
AddRecord();
break;
case 4:
DeleteRecord();
break;
case 5:
UpdateRecord();
break;
case 6:
SearchRecord();
break;
default:
cout << " Bad Choice !!!!!!" << endl << endl;
break;
}
DisplayMenu();
cin >> n_Choice;
}
if ( g_pConnection->State )
g_pConnection->Close();
g_pConnection = NULL;
CoUninitialize();
return 0;
}
void DisplayMenu()
{
cout << endl << "---------TONG XUN LU--------" << endl ;
cout << "1. Display Menu" << endl;
cout << "2. Display All Record" << endl;
cout << "3. Add A Record" << endl;
cout << "4. Delete A Record " << endl;
cout << "5. Update A Record " << endl;
cout << "6. Search A Record " << endl;
cout << "0. Exit" << endl;
cout << "----------------------------" << endl;
cout << endl << "Please Select A Choice: ";
}
BOOL DisplayAllRecord()
{
BOOL nFlag = TRUE;
try
{
g_pRecordset->Open("SELECT * FROM TXL",
g_pConnection.GetInterfacePtr(),
adOpenDynamic,
adLockOptimistic,
adCmdText);
}
catch(_com_error e)
{
cout << "Open Recordset Error: " << e.ErrorMessage() << endl;
return FALSE;
}
cout << endl << "--------+ Begin Of Record +------" << endl << endl;
cout << "ID\tName\t\t\tQQ" << endl;
while ( !g_pRecordset->adoEOF )
{
_variant_t var = g_pRecordset->GetCollect("ID");
if (var.vt != VT_NULL )
cout << (LPCSTR)_bstr_t(var) << "\t";
var = g_pRecordset->GetCollect("Name");
if ( var.vt != VT_NULL )
cout << (LPCSTR)_bstr_t(var) << "\t\t";
var = g_pRecordset->GetCollect("QQ");
if ( var.vt != VT_NULL )
cout << (LPCSTR)_bstr_t(var) << endl;
g_pRecordset->MoveNext();
}
cout << endl << "--------+ End Of Record +------" << endl << endl;
g_pRecordset->Close();
return nFlag;
}
BOOL AddRecord()
{
char strName[50];
char strQQ[20];
cout << endl << "Please Enter Your Name : ";
cin >> strName;
cout << endl << "Please Enter Your QQ: ";
cin >> strQQ;
BOOL nFlag = TRUE;
try
{
g_pRecordset->Open("SELECT * FROM TXL",
g_pConnection.GetInterfacePtr(),
adOpenDynamic,
adLockOptimistic,
adCmdText);
}
catch(_com_error e)
{
cout << "Open Recordset Error: " << e.ErrorMessage() << endl;
return FALSE;
}
g_pRecordset->AddNew();
g_pRecordset->PutCollect("Name", _variant_t(strName));
g_pRecordset->PutCollect("QQ", _variant_t(strQQ));
g_pRecordset->Update();
g_pRecordset->Close();
cout << endl << "Successfully Add A Record!" << endl << endl;
return nFlag;
}
BOOL DeleteRecord()
{
BOOL nFlag = TRUE;
long ID ;
char strSQL[256];
int nRecCnt = 0;
memset(strSQL, 0, 256);
cout << endl << "Please Select The Record ID You Want To Delete :";
cin >> ID;
sprintf(strSQL, "SELECT * FROM TXL WHERE ID = %d", ID);
try
{
g_pRecordset->Open( strSQL,
g_pConnection.GetInterfacePtr(),
adOpenDynamic,
adLockOptimistic,
adCmdText);
}
catch(_com_error e)
{
cout << "Open Recordset Error: " << e.ErrorMessage() << endl;
return FALSE;
}
while ( !g_pRecordset->adoEOF )
{
nRecCnt++;
g_pRecordset->MoveNext();
}
g_pRecordset->Close();
if ( nRecCnt == 0 )
{
cout << "The Record ID DOES NOT EXIST !!!" << endl << endl;
return FALSE;
}
sprintf(strSQL, "DELETE FROM TXL WHERE ID = %d", ID);
g_pCommand->CommandText = (_bstr_t)strSQL;
try
{
g_pCommand->Execute(NULL, NULL, adCmdText);
}
catch (_com_error e)
{
cout << "Delete Error : " << e.ErrorMessage() << endl << endl;
return FALSE;
}
cout << "Successfully Delete A Record !!!" << endl << endl;
return nFlag;
}
BOOL UpdateRecord()
{
BOOL nFlag = TRUE;
char strSQL[256];
char strName[50];
char strQQ[20];
long ID;
int nRecCnt = 0;
cout << endl << "Please Enter The Record ID You Want To Update: ";
cin >> ID;
sprintf(strSQL, "SELECT * FROM TXL WHERE ID = %d", ID);
try
{
g_pRecordset->Open( strSQL,
g_pConnection.GetInterfacePtr(),
adOpenDynamic,
adLockOptimistic,
adCmdText);
}
catch(_com_error e)
{
cout << "Open Recordset Error: " << e.ErrorMessage() << endl;
return FALSE;
}
while ( !g_pRecordset->adoEOF )
{
g_pRecordset->MoveNext();
nRecCnt++;
}
g_pRecordset->Close();
if ( nRecCnt == 0 )
{
cout << "The Record ID DOES NOT EXIST !!!" << endl << endl;
return FALSE;
}
cout << endl << "Please Enter New Name(0 No Change): " ;
cin >> strName;
cout << endl << "Please Enter New QQ(0 No Change): " ;
cin >> strQQ;
if ( (strcmp(strName, "0") == 0) && (strcmp(strQQ, "0") == 0) )
{
cout << endl << "No Record Will Be Changed." << endl << endl;
return FALSE;
}
else if ( strcmp(strQQ, "0") == 0 )
{
sprintf(strSQL, "UPDATE TXL SET Name='%s' WHERE ID=%d", strName, ID);
}
else if ( strcmp(strName, "0") == 0 )
{
sprintf(strSQL, "UPDATE TXL SET QQ='%s' WHERE ID=%d", strQQ, ID);
}
else
sprintf(strSQL, "UPDATE TXL SET Name='%s', QQ='%s' WHERE ID=%d", strName, strQQ, ID);
g_pCommand->CommandText = (_bstr_t)strSQL;
try
{
g_pCommand->Execute(NULL, NULL, adCmdText);
}
catch (_com_error e)
{
cout << "Update Record Error: " << e.ErrorMessage() << endl << endl;
return FALSE;
}
cout << "Successfully Update A Record !!!!" << endl << endl;
return nFlag;
}
void SearchRecord()
{
int nChoice;
int nRecCnt = 0;
char strName[50];
char strQQ[20];
char strSQL[256];
long ID;
memset(strSQL, 0, 256);
cout << endl << "Search Type : " << endl;
cout << "0. Search By ID [COMPLETE MATCH]" << endl;
cout << "1. Search By Name [PART MATCH]" << endl;
cout << "2. Search By QQ [COMPLETE MATCH] "<< endl;
cout << endl << "Please Select Search Type:" ;
cin >> nChoice;
switch ( nChoice )
{
case 0:
{
cout << "Please Enter The ID You Want To Search: " ;
cin >> ID;
sprintf(strSQL, "SELECT * FROM TXL WHERE ID = %d", ID);
}
break;
case 1:
{
cout << "Please Enter The Name You Want To Search: " ;
cin >> strName;
sprintf(strSQL, "SELECT * FROM TXL WHERE Name LIKE '%%%s%%'", strName);
}
break;
case 2:
{
cout << "Please Enter The QQ You Want To Search: " ;
cin >> strQQ;
sprintf(strSQL, "SELECT * FROM TXL WHERE QQ = '%s'", strQQ);
}
break;
default:
memset(strSQL, 0, 256);
cout << "Bad Search Type !!!" << endl << endl;
return;
}
if ( strlen(strSQL) == 0 )
{
cout << "Bad Search !!!" << endl << endl;
return;
}
try
{
g_pRecordset->Open(strSQL,
g_pConnection.GetInterfacePtr(),
adOpenDynamic,
adLockOptimistic,
adCmdText);
}
catch (_com_error e)
{
cout << "Error Open Recordset:" << e.ErrorMessage() << endl;
return ;
}
cout << endl << "--------------Search Result------------" << endl;
cout << "ID\tName\t\t\tQQ" << endl;
while ( !g_pRecordset->adoEOF )
{
_variant_t var = g_pRecordset->GetCollect("ID");
if (var.vt != VT_NULL )
cout << (LPCSTR)_bstr_t(var) << "\t";
var = g_pRecordset->GetCollect("Name");
if ( var.vt != VT_NULL )
cout << (LPCSTR)_bstr_t(var) << "\t\t";
var = g_pRecordset->GetCollect("QQ");
if ( var.vt != VT_NULL )
cout << (LPCSTR)_bstr_t(var) << endl;
nRecCnt++;
g_pRecordset->MoveNext();
}
cout << "---------------------------------------" << endl;
cout << nRecCnt << " Record(s) Found." << endl;
g_pRecordset->Close();
}
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