MongoDb Tutorial

Day 6 : Query document in MongoDB





Mongodb tutorial series

  1. Create database in mongodb
    2.
  2. Create collection in mongodb
    3.
  3. Create document in mongodb
    4.
  4. query document in mongodb
    5.
  5. update document in mongodb
    6.
  6. Projections in mongodb
    7.
  7. Sort records in mongodb
    8.
  8. Delete document in mongodb
    9.
  9. drop collection in mongodb
    10.
  10. drop database in mongodb
    11.


Overview

In this part of the Learn Mongo Series, we will learn how to query a document in mongodb.

find() method of mongodb


find() method in mongodb is used to query the documents from collections. Syntax is db.collection_name.find() . Examples are given below :

  • Display all documents : db.collection_name.find() method is used to print all the documents on the console as shown below : 

    											
> use students
switched to db students
> db.details.find()
{ "_id" : ObjectId("5996be4fa4b26dc0d6d75c1c"), "name" : "nodejsera", "age" : "10", "description" : "Mongodb tuttorial series" }
{ "_id" : ObjectId("5996be4fa4b26dc0d6d75c1d"), "name" : "a", "age" : "11", "description" : "learn mongodb" }
{ "_id" : ObjectId("5996be4fa4b26dc0d6d75c1e"), "name" : "b", "age" : "12", "description" : "something " }
>

  • Display documents matching a certain criteria : db.collection_name.find({search_criteria}) method is used to print all the documents on the console as shown below : 

    											
> use students
switched to db students
> db.details.find({"name": "nodejsera"})
{ "_id" : ObjectId("5996be4fa4b26dc0d6d75c1c"), "name" : "nodejsera", "age" : "10", "description" : "Mongodb tuttorial series" }
>


RDBMS where clause equivalents in mongodb


Operation Syntax Example
Equality {:} db.demo_collection.find({"name":"sophia"})
Less than {:{$lt:}} db.demo_collection.find({"age":{$lt:24}})
greater than {:{$gt:}} db.demo_collection.find({"age":{$gt:22}})
not equals {:{$ne:}} db.demo_collection.find({"age":{$ne:25}})
Less than equals {:{$lte:}} db.demo_collection.find({"age":{$lte:24}})
greater than equals {:{$gte:}} db.demo_collection.find({"age":{$gte:22}})

Summary

In this part of learn mongo series , we learned about how we can query documents from mongodb collection. We learned the following commands of mongodb :

  1. use : This command is use to either create a new database or switch to an already existing database.
  2. db.Collection_name.find() : This command is used to display all the documents in the mongodb collection.
  3. db.details.find({search_criteria}) : This command is used to display all the documents in the mongodb collection which matches the search_criteria .