mysql 前段确定查询

// 示例代码（Node.js + mysql 模块）
const mysql = require('mysql');
const connection = mysql.createConnection({
  host: 'localhost',
  user: 'user',
  password: 'password',
  database: 'database_name'
});

const userId = req.body.userId; // 用户输入
const sql = 'SELECT * FROM users WHERE id = ?';
connection.query(sql, [userId], (error, results) => {
  if (error) throw error;
  console.log(results);
});

-- 示例：添加索引
CREATE INDEX idx_user_id ON users(id);

// 示例代码（Node.js + mysql 模块）
const mysql = require('mysql');
const pool = mysql.createPool({
  connectionLimit: 10,
  host: 'localhost',
  user: 'user',
  password: 'password',
  database: 'database_name'
});

pool.getConnection((err, connection) => {
  if (err) throw err;
  connection.query('SELECT 1 + 1 AS solution', (error, results, fields) => {
    connection.release();
    if (error) throw error;
    console.log(results[0].solution);
  });
});