C++ 获取 sql server Timestamp

在 C++ 中获取 SQL Server 的 timestamp 可以通过以下步骤实现：

1. 使用 SQL Server 的 ODBC 驱动程序连接到数据库。
2. 使用 SQLPrepare 函数准备 SQL 查询语句。
3. 使用 SQLExecute 函数执行查询语句。
4. 使用 SQLBindCol 函数将 timestamp 列与 C++ 变量绑定。
5. 使用 SQLFetch 函数获取 timestamp 值。

以下是一个简单的示例代码，演示如何获取 timestamp 值：

#include <windows.h>
#include <sqlext.h>
#include <iostream>

using namespace std;

int main()
{
    SQLHENV env; // Environment Handle
    SQLHDBC dbc; // Connection Handle
    SQLHSTMT stmt; // Statement Handle
    SQLRETURN ret; // Return code

    SQL_TIMESTAMP_STRUCT timestamp; // Timestamp variable

    // Allocate an environment handle
    ret = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &env);
    if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
        cerr << "Error allocating environment handle" << endl;
        return -1;
    }

    // Set the ODBC version
    ret = SQLSetEnvAttr(env, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, 0);
    if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
        cerr << "Error setting ODBC version" << endl;
        SQLFreeHandle(SQL_HANDLE_ENV, env);
        return -1;
    }

    // Allocate a connection handle
    ret = SQLAllocHandle(SQL_HANDLE_DBC, env, &dbc);
    if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
        cerr << "Error allocating connection handle" << endl;
        SQLFreeHandle(SQL_HANDLE_ENV, env);
        return -1;
    }

    // Connect to the database
    ret = SQLConnect(dbc, (SQLCHAR*)"DataSourceName", SQL_NTS, (SQLCHAR*)"Username", SQL_NTS, (SQLCHAR*)"Password", SQL_NTS);
    if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
        cerr << "Error connecting to database" << endl;
        SQLFreeHandle(SQL_HANDLE_DBC, dbc);
        SQLFreeHandle(SQL_HANDLE_ENV, env);
        return -1;
    }

    // Allocate a statement handle
    ret = SQLAllocHandle(SQL_HANDLE_STMT, dbc, &stmt);
    if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
        cerr << "Error allocating statement handle" << endl;
        SQLDisconnect(dbc);
        SQLFreeHandle(SQL_HANDLE_DBC, dbc);
        SQLFreeHandle(SQL_HANDLE_ENV, env);
        return -1;
    }

    // Prepare the SQL query
    ret = SQLPrepare(stmt, (SQLCHAR*)"SELECT timestamp_column FROM table_name", SQL_NTS);
    if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
        cerr << "Error preparing SQL query" << endl;
        SQLFreeHandle(SQL_HANDLE_STMT, stmt);
        SQLDisconnect(dbc);
        SQLFreeHandle(SQL_HANDLE_DBC, dbc);
        SQLFreeHandle(SQL_HANDLE_ENV, env);
        return -1;
    }

    // Bind the timestamp column
    ret = SQLBindCol(stmt, 1, SQL_C_TIMESTAMP, &timestamp, sizeof(timestamp), NULL);
    if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
        cerr << "Error binding timestamp column" << endl;
        SQLFreeHandle(SQL_HANDLE_STMT, stmt);
        SQLDisconnect(dbc);
        SQLFreeHandle(SQL_HANDLE_DBC, dbc);
        SQLFreeHandle(SQL_HANDLE_ENV, env);
        return -1;
    }

    // Execute the query
    ret = SQLExecute(stmt);
    if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO && ret != SQL_NO_DATA) {
        cerr << "Error executing SQL query" << endl;
        SQLFreeHandle(SQL_HANDLE_STMT, stmt);
        SQLDisconnect(dbc);
        SQLFreeHandle(SQL_HANDLE_DBC, dbc);
        SQLFreeHandle(SQL_HANDLE_ENV, env);
        return -1;
    }

    // Fetch the timestamp value
    ret = SQLFetch(stmt);
    if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO && ret != SQL_NO_DATA) {
        cerr << "Error fetching timestamp value" << endl;
        SQLFreeHandle(SQL_HANDLE_STMT, stmt);
        SQLDisconnect(dbc);
        SQLFreeHandle(SQL_HANDLE_DBC, dbc);
        SQLFreeHandle(SQL_HANDLE_ENV, env);
        return -1;
    }

    // Display the timestamp value
    cout << "Timestamp: " << timestamp.year << "-" << timestamp.month << "-" << timestamp.day << " " << timestamp.hour << ":" << timestamp.minute << ":" << timestamp.second << endl;

    // Free the handles
    SQLFreeHandle(SQL_HANDLE_STMT, stmt);
    SQLDisconnect(dbc);
    SQLFreeHandle(SQL_HANDLE_DBC, dbc);
    SQLFreeHandle(SQL_HANDLE_ENV, env);

    return 0;
}

注意：上述代码中的 DataSourceName、Username 和 Password 需要替换为实际的值。