根据Select标签的值选择数据库中的表

<select id="tableSelect">
  <option value="table1">表1</option>
  <option value="table2">表2</option>
  <option value="table3">表3</option>
</select>

var selectElement = document.getElementById("tableSelect");
selectElement.addEventListener("change", function() {
  var selectedTable = selectElement.value;
  // 发送Ajax请求或调用后端接口，将selectedTable作为参数传递给后端
  // 后端根据selectedTable构建SQL查询语句，并执行查询操作
});

const mysql = require("mysql");

// 创建数据库连接
const connection = mysql.createConnection({
  host: "localhost",
  user: "username",
  password: "password",
  database: "database_name"
});

// 监听HTTP请求，获取前端传递的selectedTable参数
app.get("/selectTable", function(req, res) {
  const selectedTable = req.query.selectedTable;
  
  // 构建SQL查询语句
  const sql = "SELECT * FROM " + selectedTable;
  
  // 执行查询操作
  connection.query(sql, function(error, results, fields) {
    if (error) throw error;
    // 处理查询结果
    res.send(results);
  });
});

// 启动服务器
app.listen(3000, function() {
  console.log("Server is running on port 3000");
});