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MongoDB - Query Document

In this chapter, we will learn how to query documents from a MongoDB collection.

The find() Method​

To query data from a MongoDB collection, you need to use MongoDB's find() method.

Syntax​

The basic syntax of the find() method is as follows:

db.COLLECTION_NAME.find()

The find() method will display all the documents in a non-structured way.

Example​

Assume we have created a collection named mycol as follows:

> use sampleDB
switched to db sampleDB
> db.createCollection("mycol")
{ "ok" : 1 }
>

And inserted 3 documents in it using the insert() method as shown below:

> db.mycol.insert([
    {
        title: "MongoDB Overview",
        description: "MongoDB is no SQL database",
        by: "tutorials point",
        url: "http://www.tutorialspoint.com",
        tags: ["mongodb", "database", "NoSQL"],
        likes: 100
    },
    {
        title: "NoSQL Database",
        description: "NoSQL database doesn't have tables",
        by: "tutorials point",
        url: "http://www.tutorialspoint.com",
        tags: ["mongodb", "database", "NoSQL"],
        likes: 20,
        comments: [
            {
                user:"user1",
                message: "My first comment",
                dateCreated: new Date(2013,11,10,2,35),
                like: 0
            }
        ]
    }
])

Following method retrieves all the documents in the collection:

> db.mycol.find()
{ "_id" : ObjectId("5dd4e2cc0821d3b44607534c"), "title" : "MongoDB Overview", "description" : "MongoDB is no SQL database", "by" : "tutorials point", "url" : "http://www.tutorialspoint.com", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 100 }
{ "_id" : ObjectId("5dd4e2cc0821d3b44607534d"), "title" : "NoSQL Database", "description" : "NoSQL database doesn't have tables", "by" : "tutorials point", "url" : "http://www.tutorialspoint.com", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 20, "comments" : [ { "user" : "user1", "message" : "My first comment", "dateCreated" : ISODate("2013-12-09T21:05:00Z"), "like" : 0 } ] }

The pretty() Method​

To display the results in a formatted way, you can use the pretty() method.

Syntax​

db.COLLECTION_NAME.find().pretty()

Example​

Following example retrieves all the documents from the collection named mycol and arranges them in an easy-to-read format.

> db.mycol.find().pretty()
{
    "_id" : ObjectId("5dd4e2cc0821d3b44607534c"),
    "title" : "MongoDB Overview",
    "description" : "MongoDB is no SQL database",
    "by" : "tutorials point",
    "url" : "http://www.tutorialspoint.com",
    "tags" : [
        "mongodb",
        "database",
        "NoSQL"
    ],
    "likes" : 100
}
{
    "_id" : ObjectId("5dd4e2cc0821d3b44607534d"),
    "title" : "NoSQL Database",
    "description" : "NoSQL database doesn't have tables",
    "by" : "tutorials point",
    "url" : "http://www.tutorialspoint.com",
    "tags" : [
        "mongodb",
        "database",
        "NoSQL"
    ],
    "likes" : 20,
    "comments" : [
        {
            "user" : "user1",
            "message" : "My first comment",
            "dateCreated" : ISODate("2013-12-09T21:05:00Z"),
            "like" : 0
        }
    ]
}

The findOne() Method​

Apart from the find() method, there is a findOne() method, that returns only one document.

Syntax​

db.COLLECTIONNAME.findOne()

Example​

Following example retrieves the document with title "MongoDB Overview".

> db.mycol.findOne({title: "MongoDB Overview"})
{
    "_id" : ObjectId("5dd6542170fb13eec3963bf0"),
    "title" : "MongoDB Overview",
    "description" : "MongoDB is no SQL database",
    "by" : "tutorials point",
    "url" : "http://www.tutorialspoint.com",
    "tags" : [
        "mongodb",
        "database",
        "NoSQL"
    ],
    "likes" : 100
}

RDBMS Where Clause Equivalents in MongoDB​

To query the document on the basis of some condition, you can use the following operations.

Table: MongoDB Query Operators and RDBMS Equivalents​

OperationSyntaxExampleRDBMS Equivalent
Equality{<key>:{$eq:<value>}}db.mycol.find({"by":"tutorials point"}).pretty()where by = 'tutorials point'
Less Than{<key>:{$lt:<value>}}db.mycol.find({"likes":{$lt:50}}).pretty()where likes < 50
Less Than Equals{<key>:{$lte:<value>}}db.mycol.find({"likes":{$lte:50}}).pretty()where likes <= 50
Greater Than{<key>:{$gt:<value>}}db.mycol.find({"likes":{$gt:50}}).pretty()where likes > 50
Greater Than Equals{<key>:{$gte:<value>}}db.mycol.find({"likes":{$gte:50}}).pretty()where likes >= 50
Not Equals{<key>:{$ne:<value>}}db.mycol.find({"likes":{$ne:50}}).pretty()where likes != 50
Values in an array{<key>:{$in:[<value>]}}db.mycol.find({"name":{$in:["Raj", "Ram", "Raghu"]}}).pretty()Where name in ["Raj", "Ram", "Raghu"]
Values not in an array{<key>:{$nin:<value>}}db.mycol.find({"name":{$nin:["Ramu", "Raghav"]}}).pretty()Where name not in ["Ramu", "Raghav"]

AND in MongoDB​

Syntax​

To query documents based on the AND condition, you need to use the $and keyword. Following is the basic syntax of AND:

db.mycol.find({ $and: [ {<key1>:<value1>}, { <key2>:<value2>} ] })

Example​

The following example will show all the tutorials written by 'tutorials point' and whose title is 'MongoDB Overview':

> db.mycol.find({$and:[{"by":"tutorials point"},{"title": "MongoDB Overview"}]}).pretty()
{
    "_id" : ObjectId("5dd4e2cc0821d3b44607534c"),
    "title" : "MongoDB Overview",
    "description" : "MongoDB is no SQL database",
    "by" : "tutorials point",
    "url" : "http://www.tutorialspoint.com",
    "tags" : [
        "mongodb",
        "database",
        "NoSQL"
    ],
    "likes" : 100
}

OR in MongoDB​

Syntax​

To query documents based on the OR condition, you need to use the $or keyword. Following is the basic syntax of OR:

db.mycol.find(
   {
      $or: [
         {key1: value1}, {key2:value2}
      ]
   }
).pretty()

Example​

The following example will show all the tutorials written by 'tutorials point' or whose title is 'MongoDB Overview':

> db.mycol.find({$or:[{"by":"tutorials point"},{"title": "MongoDB Overview"}]}).pretty()
{
   "_id": ObjectId(7df78ad8902c),
   "title": "MongoDB Overview", 
   "description": "MongoDB is no sql database",
   "by": "tutorials point",
   "url": "http://www.tutorialsp

oint.com",
   "tags": ["mongodb", "database", "NoSQL"],
   "likes": 100
}
{
   "_id": ObjectId(7df78ad8902c),
   "title": "MongoDB Overview", 
   "description": "MongoDB is no sql database",
   "by": "XYZ",
   "url": "http://www.tutorialspoint.com",
   "tags": ["mongodb", "database", "NoSQL"],
   "likes": 20
}

Limiting Records​

To limit the records in MongoDB, you need to use the limit() method.

Syntax​

db.COLLECTION_NAME.find().limit(NUMBER)

Example​

The following example will retrieve only 2 documents:

> db.mycol.find().limit(2)
{ "_id" : ObjectId("5dd4e2cc0821d3b44607534c"), "title" : "MongoDB Overview", "description" : "MongoDB is no SQL database", "by" : "tutorials point", "url" : "http://www.tutorialspoint.com", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 100 }
{ "_id" : ObjectId("5dd4e2cc0821d3b44607534d"), "title" : "NoSQL Database", "description" : "NoSQL database doesn't have tables", "by" : "tutorials point", "url" : "http://www.tutorialspoint.com", "tags" : [ "mongodb", "database", "NoSQL" ], "likes" : 20, "comments" : [ { "user" : "user1", "message" : "My first comment", "dateCreated" : ISODate("2013-12-09T21:05:00Z"), "like" : 0 } ] }

Sorting the Results​

To sort the documents in MongoDB, you need to use the sort() method.

Syntax​

db.COLLECTION_NAME.find().sort({KEY:1})
  • 1 is for ascending order
  • -1 is for descending order

Example​

Following example will sort the documents by title in ascending order:

> db.mycol.find().sort({title:1}).pretty()
{
    "_id" : ObjectId("5dd4e2cc0821d3b44607534d"),
    "title" : "NoSQL Database",
    "description" : "NoSQL database doesn't have tables",
    "by" : "tutorials point",
    "url" : "http://www.tutorialspoint.com",
    "tags" : [
        "mongodb",
        "database",
        "NoSQL"
    ],
    "likes" : 20,
    "comments" : [
        {
            "user" : "user1",
            "message" : "My first comment",
            "dateCreated" : ISODate("2013-12-09T21:05:00Z"),
            "like" : 0
        }
    ]
}
{
    "_id" : ObjectId("5dd4e2cc0821d3b44607534c"),
    "title" : "MongoDB Overview",
    "description" : "MongoDB is no SQL database",
    "by" : "tutorials point",
    "url" : "http://www.tutorialspoint.com",
    "tags" : [
        "mongodb",
        "database",
        "NoSQL"
    ],
    "likes" : 100
}

This chapter covers the basic querying methods in MongoDB, including how to use the find(), pretty(), findOne(), limit(), and sort() methods, and how to implement conditional queries with the $and and $or operators.