mysql - 如果找不到 ID，如何插入行？

Question

我正在尝试在表格中插入用户匹配，但我不想重复。 因此，我正在运行 COUNT 查询，但是当我尝试插入新记录时，我得到了未定义，所以我无法插入记录。

我读过有关使用回调的信息，但我对 NodeJS 还很陌生，目前正在苦苦挣扎。

if(user_matches.length !== 0){
    var connection = mysql.createConnection({
        'host': 'localhost',
        'user': 'root',
        'password': '',
        'database': 'test'
    });

    connection.connect();

    //connection.query('TRUNCATE matches');
    // I was originally truncating the table, but this just doesn't cut it

    for (var x = 0; x < user_matches.length; x++){
        var countQuery = connection.query('SELECT COUNT(*) as count FROM matches WHERE user_id_1 = ?', [ user_matches[x]['user_1']['id'] ]);
        countQuery.on('result', function(){

            // Here I get the UNDEFINED error, can't insert
            connection.query('INSERT INTO matches SET ?', {
                'user_id_1': user_matches[x]['user_1']['id'],
                'user_id_2': user_matches[x]['user_2']['id']
            });

        });
    }

    connection.end();
}

Answer 1

安装async

npm install async --save

然后试试这个:

if(user_matches.length !== 0){
 var connection = mysql.createConnection({
      'host': 'localhost',
      'user': 'root',
      'password': '',
      'database': 'test'
  });

  connection.connect();

  async.each(user_matches, function(x, callback){
    var countQuery = connection.query('SELECT COUNT(*) as count FROM matches WHERE user_id_1 = ?', [ x['user_1']['id'] ]);

    countQuery.on('result', function(){
      var insertQuery = connection.query('INSERT INTO matches SET ?', {
          'user_id_1': x['user_1']['id'],
          'user_id_2': x['user_2']['id']
      });

      insertQuery.on('result', callback);

    });
  }, function(err){
    console.log('done');
  });
}