我有一个Mongo数据库,在用户集合中我只有1个文档。 我使用用户名过滤器执行find()和findOne()操作。 我得到我认为find()操作的结果不正确。MongoDB中的find()和findOne()方法显示不同的结果
MongoDB shell version: 3.2.10
connecting to: test
Server has startup warnings:
2016-10-20T20:37:32.681-0700 I CONTROL [initandlisten]
2016-10-20T20:37:32.681-0700 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2016-10-20T20:37:32.681-0700 I CONTROL [initandlisten] ** We suggest setting it to 'never'
2016-10-20T20:37:32.681-0700 I CONTROL [initandlisten]
2016-10-20T20:37:32.681-0700 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2016-10-20T20:37:32.681-0700 I CONTROL [initandlisten] ** We suggest setting it to 'never'
2016-10-20T20:37:32.681-0700 I CONTROL [initandlisten]
> use lab2
switched to db lab2
> db.users.find()
{ "_id" : ObjectId("5807ac0765f24dd0660e4332"), "username" : "avtrulzz", "fname" : "Abc", "lname" : "Def", "email" : "[email protected]", "password" : "rootuser", "mobile" : NumberLong(1234567890) }
> db.users.findOne()
{
"_id" : ObjectId("5807ac0765f24dd0660e4332"),
"username" : "avtrulzz",
"fname" : "Abc",
"lname" : "Def",
"email" : "[email protected]",
"password" : "rootuser",
"mobile" : NumberLong(1234567890)
}
> if (db.users.find({username : "noSuchUsername"})) {
... print ("Username exists");
... } else {
... print ("User does not exist"); }
Username exists
> if (db.users.findOne({username : "noSuchUsername"})) { print ("Username exists"); } else { print ("User does not exist"); }
User does not exist
> if (db.users.findOne({username : "avtrulzz"})) { print ("Username exists"); } else { print ("User does not exist"); }
Username exists
见find操作将返回用户存在这是不正确的。 findOne()表现正确。
你说的问题是前两个查询(find()与findOne())或最后一个命令(if块)的结果有差异吗?输出结果如何让你认为结果不正确? –
我认为find()还应该返回“User does not exist”,因为没有用户名称为“noSuchUsername”不存在 –