尝试使用节点从数据库进行查询，但得到“无法在调用quit后排队查询”。

Question

我对编程都很陌生。 我在我的数据库中创建了一个客户列表，并希望从中查询数据。

我不知道为什么当我连续三次运行该函数时，如果只有一个函数，它会出现错误。

var db = require('./db')


function searchClient(name, phonenumber) {
  if (phonenumber == null) {
    //when phonenumber is null
    db.query("SELECT * FROM request WHERE name LIKE '%" + name + "%'",
      function(error, results, fields) {
        if (error) throw error;
        //results with matched name
        console.log(results)
      });
  } else if (name == null) {
    //when name is null
    db.query("SELECT * FROM request WHERE phonenumber LIKE '%" + phonenumber + "%'",
      function(error, results, fields) {
        if (error) throw error;
        //results with matched phonenumber
        console.log(results)
      });
  } else {
    //when both are not null
    db.query("SELECT * FROM request WHERE (name LIKE '%" + name + "%') AND (phonenumber LIKE '%" + phonenumber + "%')",
      function(error, results, fields) {
        if (error) throw error;
        //results
        console.log(results)
      });
  }
}

db.end();


console.log('nameOnly', searchClient('aaa', null));

console.log('phonenumberOnly', searchClient(null, '4056'));

console.log('nameAndPhonenumberBoth', searchClient('Engname', '3330'));

我从终端

获得此结果

nameOnly undefined
phonenumberOnly undefined
nameAndPhonenumberBoth undefined
/home/ubuntu/fixnow/api/search.js:9
      if (error) throw error;
                 ^

Error: Cannot enqueue Query after invoking quit.
    at Protocol._validateEnqueue (/home/ubuntu/fixnow/node_modules/mysql/lib/protocol/Protocol.js:202:16)
    at Protocol._enqueue (/home/ubuntu/fixnow/node_modules/mysql/lib/protocol/Protocol.js:135:13)
    at Connection.query (/home/ubuntu/fixnow/node_modules/mysql/lib/Connection.js:208:25)
    at searchClient (/home/ubuntu/fixnow/api/search.js:7:8)
    at Object.<anonymous> (/home/ubuntu/fixnow/api/search.js:35:25)
    at Module._compile (module.js:570:32)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)

任何人都可以帮助我 如果你能提出任何简明的代码，请告诉我。