MongoDB findById返回文档列表而不是单个结果？如何只获取一个文档？
要仅获得单个结果，请findOne()在id的基础上使用和提取。让我们创建一个包含文档的集合-
> db.demo340.insertOne({_id:1,"Name":"Chris",Age:21});
{ "acknowledged" : true, "insertedId" : 1 }
> db.demo340.insertOne({_id:2,"Name":"David",Age:23});
{ "acknowledged" : true, "insertedId" : 2 }
> db.demo340.insertOne({_id:3,"Name":"Bob",Age:20});
{ "acknowledged" : true, "insertedId" : 3 }
> db.demo340.insertOne({_id:4,"Name":"Sam",Age:19});
{ "acknowledged" : true, "insertedId" : 4 }在find()方法的帮助下显示集合中的所有文档-
> db.demo340.find();
这将产生以下输出-
{ "_id" : 1, "Name" : "Chris", "Age" : 21 }
{ "_id" : 2, "Name" : "David", "Age" : 23 }
{ "_id" : 3, "Name" : "Bob", "Age" : 20 }
{ "_id" : 4, "Name" : "Sam", "Age" : 19 }这是findbyid的查询-
> db.demo340.findOne({_id:1});这将产生以下输出-
{ "_id" : 1, "Name" : "Chris", "Age" : 21 }