Question

VC++6.0通过MFC 创建了 对话框 ，然后怎样通过SQL Server 连接到数据库？

我用VC++创建了几个关联的对话框，然后我想连接到SQL Server数据库，该怎么办？我已经创建了一个数据库Library ，数据源也已经配置好了。

Answer 1

class DBConnection
{
public:
DBConnection(void);
~DBConnection(void);
int OpenConnect(void);
int ExecuteSQL(_bstr_t strCmd);
_RecordsetPtr GetRecondSetPrt();
private:
_ConnectionPtr m_pConnection; //链接数据库德指针变量
_RecordsetPtr m_pRecordset; //指向记录集的指针
_variant_t RecordsAffected; //受影响的记录条数
};

DBConnection::DBConnection(void)
{
m_pConnection=NULL;
m_pRecordset=NULL;
}

DBConnection::~DBConnection(void)
{
m_pConnection=NULL;
m_pRecordset=NULL;
}

//打开数据库链接
int DBConnection::OpenConnect(void)
{
try
{
//创建连接对象
m_pConnection.CreateInstance("ADODB.Connection");

//设置连接字符串

_bstr_t strConnect ="Provider=SQLOLEDB;Data Source=20110121-1545\\SQLEXPRESS;\
Initial Catalog=ExpManDB;User ID=sa;PWD=123";

//设置连接超时时间为5秒
m_pConnection->ConnectionTimeout = 5;

//连接数据库
m_pConnection->Open(strConnect, "", "", adModeUnknown);
return 1;

}
catch(_com_error e)
{
CString errorMsg;
errorMsg.Format(_T("连接数据库失败!\r错误信息:%s"),(LPCSTR)e.ErrorMessage());
AfxMessageBox(errorMsg);
return 0;
}
}

//返回受影响的记录条数
int DBConnection::ExecuteSQL(_bstr_t strCmd)
{
if(m_pConnection->State)
{
try
{
m_pRecordset.CreateInstance("ADODB.Recordset"); //为Recordset对象创建实例
//执行SQL语句，并返回受影响的记录条数
m_pRecordset=m_pConnection->Execute(strCmd,&RecordsAffected,adCmdText);
return RecordsAffected.intVal;
}
catch(_com_error &e)
{
AfxMessageBox(e.Description());
return 0;
}
}
return 0;
}

//返回记录集以便后续使用
_RecordsetPtr DBConnection::GetRecondSetPrt()
{
return m_pRecordset;
}
可以像这样使用，strCmd为sql语句
DBConnection dbConnector;
if(dbConnector.OpenConnect() == 0)
{
return;
}
if(dbConnector.ExecuteSQL((_bstr_t)strCmd) == 0)
{
return;
}
当然如果你还需要取出数据的时候可以这样用
_RecordsetPtr pRecordSet;
pRecordSet=dbConnector.GetRecondSetPrt();
_variant_t vCardNo;
vCardNo = pRecordSet->GetCollect("cardNO"); //得到数据表种cardNO字段
后面_variant_t类型就可以转换为int float CString等各种类型了。
如果有什么问题再交流。

Answer 2

你可以创建一个数据连接的公共类：DataBase
这样就很方便在其它类来使用它了。
DataBase::DataBase()
{
}

DataBase::~DataBase()
{
}

void DataBase::ConnectDB()//创建连接
{
::CoInitialize(NULL);
try{
m_pConnection.CreateInstance("ADODB.Connection");///创建Connection对象
_bstr_t str = "Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=Library ;";//Library是你的数据库名
this->m_pConnection->Open(str, "sa", "sa", adModeUnknown);
}catch(_com_error e){
AfxMessageBox("connect error!");
}
}

bool DataBase::ExecuteQuery(CString sql)//执行查询
{
_bstr_t bSql = sql;
try{
this->m_pRecordset = m_pConnection->Execute(bSql,NULL,adCmdText);
}catch(_com_error e){
//AfxMessageBox("Recordset error!");
return false;
}
return true;
}

bool DataBase::Close()
{
return (!FAILED(m_pRecordset->Close()));
}
在其它类调用时：DataBase db;
db.ConnectDB();
CString sql = "select * from xxTable";
db.ExecuteQuery(sql);
db.Close();

Answer 3

LINUX / ODBC / MYSQL

#ifdef WIN32
#include <windows.h>
#include <odbcinst.h>
#include <sqlext.h>
#else
#include <mysql.h>
#include <unistd.h>
#define SQLHANDLE static MYSQL
#endif
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

SQLHANDLE hDBEnv, hDBC;

int DB_Open(char * dbcn, char * usr, char * pwd)
{
int r;
#ifdef WIN32
r = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &hDBEnv);
if(r) return 0;
r = SQLSetEnvAttr(hDBEnv,SQL_ATTR_ODBC_VERSION,
(void*)SQL_OV_ODBC3,0);
if(r) return 0;
r = SQLAllocHandle(SQL_HANDLE_DBC, hDBEnv, &hDBC);
if(r) return 0;
r = SQLConnect(hDBC,
(unsigned char *)dbcn, strlen(dbcn),
(unsigned char *)usr, strlen(usr),
(unsigned char *)pwd, strlen(pwd));
return r==SQL_SUCCESS || r==SQL_SUCCESS_WITH_INFO;
#else
mysql_init(&hDBC);
MYSQL * rx = mysql_real_connect(
&hDBC, dbcn, usr, pwd, NULL, 0, NULL, 0);
if(!rx) return 0;
return 1;
#endif
}//end DB_Open

int DB_Exec(char * sql)
{
#ifdef WIN32
SQLHANDLE hStatement = NULL;
SQLAllocHandle(SQL_HANDLE_STMT, hDBC, &hStatement);
SQLExecDirect(hStatement,(unsigned char *)sql, strlen(sql));
SQLCloseCursor(hStatement);
SQLFreeHandle(SQL_HANDLE_STMT, hStatement);
hStatement = NULL;
#else
mysql_real_query (&hDBC, sql, strlen(sql));
#endif
return 1;
}//end DB_Exec

int DB_Close(void)
{
#ifdef WIN32
SQLDisconnect(hDBC);
SQLFreeHandle(SQL_HANDLE_DBC, hDBC);
SQLFreeHandle(SQL_HANDLE_ENV, hDBEnv);
#else
mysql_close(&hDBC);
#endif
return 1;
}//DB_Close()

#ifndef WIN32
typedef struct tagMySQLRecordset {
MYSQL_RES * hRecord;
void * * row;
int * size;
int cols;
} MYSQLRecordset;

#endif

void DB_CleanQuery(void *hRecordset)
{
if(!hRecordset) return;
#ifdef WIN32
__try {
SQLCloseCursor(hRecordset);
SQLFreeHandle(SQL_HANDLE_STMT, hRecordset);
hRecordset = NULL;
}__finally{
return;
}//end try
#else
MYSQLRecordset * hRec = (MYSQLRecordset *) hRecordset;
mysql_free_result (hRec->hRecord);
free(hRec->row); hRec->row = NULL;
free(hRec->size); hRec->size = NULL;
free(hRec); hRec = NULL;
#endif
}//end DB_CleanQuery

int DB_Next(void * hRecordset)
{
int r=0; if(!hRecordset) return 0;
#ifdef WIN32
r = SQLFetch(hRecordset);
r = r == SQL_SUCCESS || r == SQL_SUCCESS_WITH_INFO;
if(!r) {
DB_CleanQuery(hRecordset);
}//end if
#else
MYSQLRecordset * hRec = (MYSQLRecordset *) hRecordset;
MYSQL_ROW row = mysql_fetch_row (hRec->hRecord);
if(row) {
for(int i=0; i<hRec->cols; i++) {
memcpy(hRec->row[i], row[i], hRec->size[i]);
}//next i
r = 1;
}else{
DB_CleanQuery(hRecordset);
r = 0;
}//end if
#endif
return r;
}//end DB_Next

int DB_params_count(const char * fmt)
{
int i=0, j=0;
while(fmt[i]) {
if(fmt[i]=='%') j++;
i++;
}//end while
return j;
}//end DB_params_count

void * DB_Query(char *sql, const char *fmt, ...)
{
int r=0;
int cols = DB_params_count(fmt);
if(cols<1) return NULL;
#ifdef WIN32
SQLHANDLE hStatement = NULL;
SQLAllocHandle(SQL_HANDLE_STMT, hDBC, &hStatement);
r = SQLExecDirect(hStatement,(unsigned char *)sql, strlen(sql));
r = r==SQL_SUCCESS || r == SQL_SUCCESS_WITH_INFO;
if(!r) {
return NULL;
}//end if
#else
r = mysql_real_query (&hDBC, sql, strlen(sql));
if(r) return NULL;
MYSQL_RES * rec = NULL;
rec = mysql_store_result (&hDBC);
if(!rec) return NULL;
MYSQLRecordset * hStatement
= (MYSQLRecordset *)malloc(sizeof(MYSQLRecordset));
if(!hStatement) return NULL;
memset(hStatement, 0, sizeof(MYSQLRecordset));
hStatement->hRecord = rec;
hStatement->cols = cols;
hStatement->row = (void **)malloc(cols * sizeof(void *));
memset(hStatement->row, 0, cols * sizeof(void *));
hStatement->size = (int *)malloc(cols * sizeof(int));
memset(hStatement->size, 0, cols * sizeof(int));
#endif
va_list ap; va_start(ap, fmt);
void * var; char buf[32];
int i=0,j=0,k=0,sz=0; char c=0;
int len = strlen(fmt); int bad=1;
#ifdef WIN32
int col=1;
#else
int col=0;
#endif
while(fmt[i]) {
c = fmt[i++];
if(c != '%') continue;
c = fmt[i++];
var = va_arg(ap, void *);
if(c == 'd') {
#ifdef WIN32
SQLBindCol(hStatement, col, SQL_C_SLONG, var, 4,NULL);
#else
hStatement->row[col] = var;
hStatement->size[col] = sizeof(long);
#endif
col++;
continue;
}//end if
if(c == 'f') {
#ifdef WIN32
SQLBindCol(hStatement, col, SQL_C_FLOAT, var, 4,NULL);
#else
hStatement->row[col] = var;
hStatement->size[col] = sizeof(float);
#endif
col++;
continue;
}//end if
memset(buf, 0, 32); bad=1;
for(j=i-1; j<len; j++) {
c = fmt[j];
if(c>='0' && c<='9') buf[j-i+1]=c;
if(c=='s')
}//next j
if(bad) return NULL;
sscanf(buf, "%d", &sz);
#ifdef WIN32
SQLBindCol(hStatement, col, SQL_C_CHAR, var, sz, NULL);
#else
hStatement->row[col] = var;
hStatement->size[col] = sz;
#endif
col++;
i = k;
}//end while
va_end(ap);
return hStatement;
}//end DB_Rec