限制MongoDB中返回的数据以仅显示文档中的特定值
要限制返回的数据，请使用find()。字段的值0和1将决定什么字段值可见或隐藏。
让我们创建一个包含文档的集合-
> db.demo330.insertOne({"Id":101,"Name":"Chris","Age":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e52149ff8647eb59e562081")
}
> db.demo330.insertOne({"Id":102,"Name":"Sam","Age":24});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e5214aaf8647eb59e562082")
}
> db.demo330.insertOne({"Id":103,"Name":"David","Age":28});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e5214b3f8647eb59e562083")
}
> db.demo330.insertOne({"Id":104,"Name":"Bob","Age":23});
.
{
"acknowledged" : true,
"insertedId" : ObjectId("5e5214bdf8647eb59e562084")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo330.find();
这将产生以下输出-
{ "_id" : ObjectId("5e52149ff8647eb59e562081"), "Id" : 101, "Name" : "Chris", "Age" : 21 }
{ "_id" : ObjectId("5e5214aaf8647eb59e562082"), "Id" : 102, "Name" : "Sam", "Age" : 24 }
{ "_id" : ObjectId("5e5214b3f8647eb59e562083"), "Id" : 103, "Name" : "David", "Age" : 28 }
{ "_id" : ObjectId("5e5214bdf8647eb59e562084"), "Id" : 104, "Name" : "Bob", "Age" : 23 }以下是限制MongoDB中返回数据的查询。由于设置了1，因此只有字段“名称”可见-
> db.demo330.find({},{Name:1});这将产生以下输出-
{ "_id" : ObjectId("5e52149ff8647eb59e562081"), "Name" : "Chris" }
{ "_id" : ObjectId("5e5214aaf8647eb59e562082"), "Name" : "Sam" }
{ "_id" : ObjectId("5e5214b3f8647eb59e562083"), "Name" : "David" }
{ "_id" : ObjectId("5e5214bdf8647eb59e562084"), "Name" : "Bob" }