我有一个Mongo用户数据库，我正在用Mongoose查询.我想做findOne来确定用户是否已经存在.我想让它先搜索一个用户是否已经有邮箱，如果没有，它应该搜索一个用户是否有手机.这必须在两个单独的查询中完成，还是可以合并成一个查询？
User.findOne({ email: req.body.email }).exec(function(err, user){
if (user) //user already exists with email
else //no users with that email but we haven't checked phone number yet!
});
为什么不直接使用$or操作符呢？
User.findOne({$or: [
{email: req.body.email},
{phone: req.body.phone}
]}).exec(function(err, user){
if (user) {} //user already exists with email AND/OR phone.
else {} //no users with that email NOR phone exist.
});
以下是伪SQL的等效值:
SELECT * FROM users WHERE email = '%1' OR phone = '%2'