在MongoDB中对内部项目进行数组索引或索引以获取值
首先，让我们创建一个包含文档的集合，并使用sureIndex()创建一个索引-
> db.demo323.insertOne({"details":{"Name":"Chris","Age":34}});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e51157af8647eb59e56206e")
}
> db.demo323.insertOne({"details":{"Name":"David","Age":31}});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e511581f8647eb59e56206f")
}
> db.demo323.insertOne({"details":{"Name":"Bob","Age":28}});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e511589f8647eb59e562070")
}
> db.demo323.ensureIndex({"details.Name":1});
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 2,
"numIndexesAfter" : 3,
"ok" : 1
}在find()方法的帮助下显示集合中的所有文档-
> db.demo323.find();
这将产生以下输出-
{ "_id" : ObjectId("5e51157af8647eb59e56206e"), "details" : { "Name" : "Chris", "Age" : 34 } }
{ "_id" : ObjectId("5e511581f8647eb59e56206f"), "details" : { "Name" : "David", "Age" : 31 } }
{ "_id" : ObjectId("5e511589f8647eb59e562070"), "details" : { "Name" : "Bob", "Age" : 28 } }以下是从数组中查找值的查询-
> db.demo323.find({"details.Name":"Bob"});这将产生以下输出-
{ "_id" : ObjectId("5e511589f8647eb59e562070"), "details" : { "Name" : "Bob", "Age" : 28 } }