使用变量插入到SELECT中

<?php
$userId = $_GET['userId']; // 从URL参数中获取变量值

// 使用变量插入到SELECT中
$sql = "SELECT * FROM users WHERE id = $userId";

// 执行查询语句
$result = mysqli_query($conn, $sql);

// 处理查询结果
while ($row = mysqli_fetch_assoc($result)) {
    // 输出查询结果
    echo "User ID: " . $row['id'] . "<br>";
    echo "User Name: " . $row['name'] . "<br>";
    // ...
}

// 关闭数据库连接
mysqli_close($conn);
?>

import sqlite3

userId = input("Enter user ID: ")  # 从用户输入中获取变量值

# 使用变量插入到SELECT中
sql = "SELECT * FROM users WHERE id = ?"

# 连接数据库
conn = sqlite3.connect('database.db')
cursor = conn.cursor()

# 执行查询语句
cursor.execute(sql, (userId,))

# 处理查询结果
rows = cursor.fetchall()
for row in rows:
    # 输出查询结果
    print("User ID:", row[0])
    print("User Name:", row[1])
    # ...

# 关闭数据库连接
conn.close()

import java.sql.*;

public class Main {
    public static void main(String[] args) {
        int userId = 123; // 假设变量值为123

        // 使用变量插入到SELECT中
        String sql = "SELECT * FROM users WHERE id = ?";

        // 连接数据库
        try (Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe", "username", "password");
             PreparedStatement stmt = conn.prepareStatement(sql)) {

            // 设置变量值
            stmt.setInt(1, userId);

            // 执行查询语句
            ResultSet rs = stmt.executeQuery();

            // 处理查询结果
            while (rs.next()) {
                // 输出查询结果
                System.out.println("User ID: " + rs.getInt("id"));
                System.out.println("User Name: " + rs.getString("name"));
                // ...
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}