MongoDB切片数组在填充字段？
> db.demo503.insertOne({_id:1,Name:"John",Subject:["MySQL","Java","C"]});
{ "acknowledged" : true, "insertedId" : 1 }
> db.demo503.insertOne({_id:2,Name:"David",Subject:["MongoDB","C++","Python"]});
{ "acknowledged" : true, "insertedId" : 2 }在find()方法的帮助下显示集合中的所有文档-
> db.demo503.find().pretty();
这将产生以下输出-
{ "_id" : 1, "Name" : "John", "Subject" : [ "MySQL", "Java", "C" ] }
{
"_id" : 2,
"Name" : "David",
"Subject" : [
"MongoDB",
"C++",
"Python"
]
}以下是对填充字段中的切片数组的查询-
> db.demo503.find({_id:2}, { 'Subject': { $slice: -1 }});这将产生以下输出-
{ "_id" : 2, "Name" : "David", "Subject" : [ "Python" ] }