How to query mongodb Document in a collection ?

18 Jul 2020 oracleappsadmin

The tutorial provides the different methods available to Query document in MongoDB collection. A document can be read or queried in mongodb using find() , findOne(), pretty() methods which we will discuss in detail with examples.

Query document methods in MongoDB

Method Name – find() :

Syntax: > db.collectionName.find()

The find() method is the basic method to query the document in a collection. This method lists down all the documents available in a collection.

Insert the document in the Collection – oracleappsUsers

> db.oracelappsUsers.insert({
… name: "Rohit Verma",
… userType: "Subscriber",
… description: "MongoDB insert document Tutorial",
… createdBy: "oracelappshelp.com"
… })
WriteResult({ "nInserted" : 1 })

Query the document with find () in the collection – oracleappsUsers. It will list down all the available documents.

> db.oracelappsUsers.find()
{ "_id" : ObjectId("5f12fd48d4a587e31cddd7e5"), "name" : "Mohit Sharma", "userType" : "Admin", "description" : "MongoDB insert document sample", "createdBy" : "oracelappshelp.com" }
{ "_id" : ObjectId("5f130f1c3a96070d59afd2c0"), "name" : "Rohit Verma", "userType" : "Subscriber", "description" : "MongoDB insert document Tutorial", "createdBy" : "oracelappshelp.com" }

Method Name – pretty

Syntax – >db.collectionName.find().pretty()

The pretty() method is allowed to format the Query document result. The below given is the example for find().pretty()

> db.oracelappsUsers.find().pretty()
{
"_id" : ObjectId("5f12fd48d4a587e31cddd7e5"),
"name" : "Mohit Sharma",
"userType" : "Admin",
"description" : "MongoDB insert document sample",
"createdBy" : "oracelappshelp.com"
}
{
"_id" : ObjectId("5f130f1c3a96070d59afd2c0"),
"name" : "Rohit Verma",
"userType" : "Subscriber",
"description" : "MongoDB insert document Tutorial",
"createdBy" : "oracelappshelp.com"
}

Method Name – findOne()

Syntax – >db.collectionName.findOne(<search_attribute>)

The findOne() method in MongoDB allows to query a single document by providing the document attribute details. The below given example depicts the usage of findOne() to query document in a collection.

> db.oracelappsUsers.findOne({name: "Mohit Sharma"})
{
"_id" : ObjectId("5f12fd48d4a587e31cddd7e5"),
"name" : "Mohit Sharma",
"userType" : "Admin",
"description" : "MongoDB insert document sample",
"createdBy" : "oracelappshelp.com"
}

Query Operators in MongoDB

RDBMS provides various operators to retrieve the data based on specified conditions like Where , <= , >= , AND , OR

MongoDB provides the RDBMS equivalent operators to query the document in a collection.

S. No RDBMS Search Data Query MongoDB Query Document
1 SELECT * from Orders db.orders.find( {} )
2 SELECT * FROM orders WHERE status = “COMPLETED” db.orders.find( { status: “COMPLETED” } )
3 SELECT * FROM orders WHERE status in (“INPROGRESS”, “PENDING”) db.orders.find( { status: { $in: [ “INPROGRESS”, “PENDING” ] } } )
4 SELECT * FROM orders WHERE status = “PENDING” AND price < 2000 db.orders.find( { status: “PENDING”, price: { $lt: 2000 } } )
5 SELECT * FROM orders WHERE status = “PENDING” OR price < 2000 db.orders.find( { $or: [ { status: “PENDING” }, { price: { $lt: 2000 } } ] } )
6 SELECT * FROM orders WHERE status = “PENDING” AND ( price < 3000 OR item LIKE “Laptop%”) db.orders.find( {
status: “PENDING”,
$or: [ { price: { $lt: 3000 } }, { item: /^Laptop/ } ]
} )