Querying/Finding/Selecting Dcouments in MongoDB

Finding The Document

• MongoDB provides db.collection.find() method to read documents from a collection.

  Syntax:-

  db.collection.find(query, projection)

  Parameter	Type	Description
  query	document	Optional. Specifies selection filter using query operators. To return all documents in a collection, omit this parameter or pass an empty document ({}).
  projection	document	Optional. The projection parameter determines which fields are returned in the matching documents. { field1: 1or0, field2: 1or0 ... }

  Note:- Please refer WildCard/RegEx section in this tutorial for better query making

  Example:-
  

  List all entries of ‘users’ collection

  >db.users.find()

  Output:-

  {"_id" :ObjectId("5774adbcfc520de27ab8744e"),"userid" : "Alex",
  "Age" : 25,"gamesplayed" : ["Rummy","TeenPati"]} { "_id" :ObjectId("5774ae18fc520de27ab8744f"), "userid" : "Andrew",
  "Age" : 40, "gamesplayed" : [ ], "totalbet" : 0,"totalwin" :0}

  List userids from ‘users’ collection

  >db.users.find({},{userid:1}).pretty()

  Output:-

   {"_id" : ObjectId("5774adbcfc520de27ab8744e"),
   "userid" : "Alex"}
   {"_id" : ObjectId("5774ae18fc520de27ab8744f"),
   "userid" : "Andrew"}
    

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