创建两个连接不行吗？

var connection1 = mysql.createConnection({
  host     : 'localhost',
  user     : 'me',
  password : 'secret',
  database : 'my_db1'
});

var connection2 = mysql.createConnection({
  host     : 'localhost',
  user     : 'me',
  password : 'secret',
  database : 'my_db2'
});

@DominicHjj 是的，

var result1 = connection1.query('sql');
connection2.save('update table set col = ?', [result1.rows.length]);

类似这样，一个connection操作一个库

MySQL offers a changeUser command that allows you to alter the current user and other aspects of the connection without shutting down the underlying socket:

connection.changeUser({user : 'john'}, function(err) {
  if (err) throw err;
});

The available options for this feature are:

user: The name of the new user (defaults to the previous one). password: The password of the new user (defaults to the previous one). charset: The new charset (defaults to the previous one). database: The new database (defaults to the previous one).