使用 Visual C 连接到 MSSQL Server Express 并提取一些表数据的最少代码表达

Question

我的计算机上安装了以下软件：

• Microsoft SQL Server Express 2005
• Microsoft Visual C++ Express 2008

我有一个 .mdf 文件，我需要从中读取一些数据并将其转储到文本文件。我可以使用 Visual Studio 中的数据库资源管理器浏览数据库文件，没有任何问题，但从应用程序连接时遇到问题。

我广泛搜索，几乎所有“解决方案”都说我应该开始一个新项目并选择“SQL Server 应用程序模板”，而我在模板中没有该模板。我发现的其他教程说我应该使用“数据源配置向导”，但是我在任何菜单中都找不到这样的向导。

我不介意点击，尽管我更希望所有这些都可以用纯 C++ 代码实现。比如：

DbConnection *d = new MSSQLConnection("local", "c:\path\to\file.mdf");
DbQuery *q = new DbQuery(d, "select * from mytable");
...dump the data and go home

谢谢。

或者，如果有人可以告诉我如何在 C++ 中执行此操作：

http:// Sharpertutorials.com/connecting-to-a-sql-server-database/

Answer 1

就是这样。一旦你知道了，就非常简单和容易......

SqlConnection^ myConnection = gcnew SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=\"file.mdf\";Integrated Security=True;Connect Timeout=10;User Instance=True");
myConnection->Open();

SqlCommand^ scmd = gcnew SqlCommand("select ID from atable", myConnection);
SqlDataReader^ r = scmd->ExecuteReader();
while (r->Read())
    __int64 id = r->GetInt64(0);
r->Close();

Answer 2

这对我有用

#include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <sqltypes.h>
#include <sql.h>
#include <sqlext.h>

using namespace std;

int main() {
    #define SQL_RESULT_LEN 240
    #define SQL_RETURN_CODE_LEN 1000
    //define handles and variables
    SQLHANDLE sqlConnHandle;
    SQLHANDLE sqlStmtHandle;
    SQLHANDLE sqlEnvHandle;
    SQLWCHAR retconstring[SQL_RETURN_CODE_LEN];
    //initializations
    sqlConnHandle = NULL;
    sqlStmtHandle = NULL;
    //allocations
    if (SQL_SUCCESS != SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &sqlEnvHandle))
        goto COMPLETED;
    if (SQL_SUCCESS != SQLSetEnvAttr(sqlEnvHandle, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, 0))
        goto COMPLETED;
    if (SQL_SUCCESS != SQLAllocHandle(SQL_HANDLE_DBC, sqlEnvHandle, &sqlConnHandle))
        goto COMPLETED;
    //output
    cout << "Attempting connection to SQL Server...";
    cout << "\n";
    //connect to SQL Server  
    //I am using a trusted connection and port 14808
    //it does not matter if you are using default or named instance
    //just make sure you define the server name and the port
    //You have the option to use a username/password instead of a trusted     connection
    //but is more secure to use a trusted connection
    switch (SQLDriverConnectW(sqlConnHandle,
        NULL,
        (SQLWCHAR*)L"DRIVER={SQL Server};SERVER=ServerAddress,     1433;DATABASE=DataBaseName;UID=DataBaseUserName;PWD=PassWord;",
        //(SQLWCHAR*)L"DRIVER={SQL Server};SERVER=localhost, 1433;DATABASE=master;Trusted=true;",
        SQL_NTS,
        retconstring,
        1024,
        NULL,
        SQL_DRIVER_NOPROMPT)) {
    case SQL_SUCCESS:
        cout << "Successfully connected to SQL Server";
        cout << "\n";
        break;
    case SQL_SUCCESS_WITH_INFO:
        cout << "Successfully connected to SQL Server";
        cout << "\n";
        break;
    case SQL_INVALID_HANDLE:
        cout << "Could not connect to SQL Server";
        cout << "\n";
        goto COMPLETED;
    case SQL_ERROR:
        cout << "Could not connect to SQL Server";
        cout << "\n";
        goto COMPLETED;
    default:
        break;
    }
    //if there is a problem connecting then exit application
    if (SQL_SUCCESS != SQLAllocHandle(SQL_HANDLE_STMT, sqlConnHandle,     &sqlStmtHandle))
        goto COMPLETED;
    //output
    cout << "\n";
    cout << "Executing T-SQL query...";
    cout << "\n";
    //if there is a problem executing the query then exit application
    //else display query result
    if (SQL_SUCCESS != SQLExecDirectW(sqlStmtHandle, (SQLWCHAR*)L"SELECT @@VERSION", SQL_NTS)) {
        cout << "Error querying SQL Server";
        cout << "\n";
        goto COMPLETED;
    }
    else {
        //declare output variable and pointer
        SQLCHAR sqlVersion[SQL_RESULT_LEN];
        SQLINTEGER ptrSqlVersion;
        while (SQLFetch(sqlStmtHandle) == SQL_SUCCESS) {
            SQLGetData(sqlStmtHandle, 1, SQL_CHAR, sqlVersion,     SQL_RESULT_LEN, &ptrSqlVersion);
            //display query result
            cout << "\nQuery Result:\n\n";
            cout << sqlVersion << endl;
        }
    }
    //close connection and free resources
COMPLETED:
    SQLFreeHandle(SQL_HANDLE_STMT, sqlStmtHandle);
    SQLDisconnect(sqlConnHandle);
    SQLFreeHandle(SQL_HANDLE_DBC, sqlConnHandle);
    SQLFreeHandle(SQL_HANDLE_ENV, sqlEnvHandle);
    //pause the console window - exit when key is pressed
    cout << "\nPress any key to exit...";
    getchar();
}