MongoDB中有什么方法可以获取json数据的内部值？
要获取JSON数据的内部值，请find()与dot（。）表示法一起使用。让我们创建一个包含文档的集合-
> db.demo235.insertOne(
... {
... "id":101,
... "details":[
... {
... "Name":"Chris Brown",
... "Age":21
... },
... {
... "Name":"David Miller",
... "Age":24
... }
... ],
... "otherdetails":[
... {
... "Score":56,
... "Subject":"MongoDB"
... },
... {
... "Score":78,
... "Subject":"MySQL"
... }
... ]
... }
...);
{
"acknowledged" : true,
"insertedId" : ObjectId("5e418d22f4cebbeaebec514b")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo235.find().pretty();
这将产生以下输出-
{
"_id" : ObjectId("5e418d22f4cebbeaebec514b"),
"id" : 101,
"details" : [
{
"Name" : "Chris Brown",
"Age" : 21
},
{
"Name" : "David Miller",
"Age" : 24
}
],
"otherdetails" : [
{
"Score" : 56,
"Subject" : "MongoDB"
},
{
"Score" : 78,
"Subject" : "MySQL"
}
]
}以下是获取json数据的内部值的查询-
> db.demo235.find({},{"otherdetails.Subject":1,_id:0});这将产生以下输出-
{ "otherdetails" : [ { "Subject" : "MongoDB" }, { "Subject" : "MySQL" } ] }