如何检查有字段有值的单据是否存在并返回true/false？

const mysql = require('mysql');

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

// 连接到数据库
connection.connect();

// 定义要检查的单据类型和字段
const tableName = 'invoices';
const fieldName = 'amount';

// 构建查询语句
const query = `SELECT COUNT(*) AS count FROM ${tableName} WHERE ${fieldName} IS NOT NULL`;

// 执行查询语句
connection.query(query, (error, results) => {
  if (error) throw error;

  // 获取查询结果
  const count = results[0].count;

  // 判断字段是否有值
  const exists = count > 0;

  // 打印结果
  console.log(`字段${fieldName}是否有值的单据存在：${exists}`);

  // 关闭数据库连接
  connection.end();
});