Create MongoDb view contain find clause - mongodb

Question

Imagine I have a collection named user with below fields
- name
- family
- age
and I want to create a view that return all users that are 19 and 21

Answer 1

try
db.createView( "viewName", "collection", [
{ $match : { key : value } }
,...
,...
])

Answer 2

OK let's start by adding some data to a users collection, lets have a few people at diffrent ages:
> db.users.insertMany([
... { "name": "foo", age: 12 },
... { "name": "bar", age: 19 },
... { "name": "wibble", age: 20 },
... { "name": "wobble", age: 21 }
... ]);
{
"acknowledged" : true,
"insertedIds" : [
ObjectId("5bd18277289332325f377fff"),
ObjectId("5bd18277289332325f378000"),
ObjectId("5bd18277289332325f378001"),
ObjectId("5bd18277289332325f378002")
]
}
We can then write a view on top of this collection using the createView method which takes in a aggregation pipeline:
> var pipelines = [ { "$match" : { "$or" : [ { "age" : 19 }, { "age" :21 } ] } } ];
> db.createView("users19and21", "users", pipelines);
{ "ok" : 1 }
If you want to test your pipeline out before creating the view you can just call the aggregate method on the users collection, for example:
> var pipelines = [ { "$match" : { "$or" : [ { "age" : 19 }, { "age" :21 } ] } } ];
> db.users.aggregate(pipelines);
{ "_id" : ObjectId("5bd18277289332325f378000"), "name" : "bar", "age" : 19 }
{ "_id" : ObjectId("5bd18277289332325f378002"), "name" : "wobble", "age" : 21 }
Once we have our view we can just query it like a collection:
> db.users19and21.find()
{ "_id" : ObjectId("5bd18277289332325f378000"), "name" : "bar", "age" : 19 }
{ "_id" : ObjectId("5bd18277289332325f378002"), "name" : "wobble", "age" : 21 }
More information on creating views in mongodb can be found on their documentation - https://docs.mongodb.com/manual/reference/method/db.createView/