Query Document using find() method In MongoDB

MongoDB Query Document using find() method

In my previous tutorials I have used the find() method to query all the documents from a collection.

In this tutorial, we will see the usage of find() method to query the documents from a collection based on the given criteria. Lets get started.

Querying all the documents in JSON format

Lets say we have a collection “employee” in a database named “employeeDB”. To get all the documents we use this command:

db.employee.find()

However the output we get is not in any format and less-readable. To improve the readability, we can format the output in JSON format with this command:

db.employee.find().forEach(printjson);

OR simply use pretty() – It does the same thing.

db.employee.find().pretty()

Query Document based on the criteria

Instead of fetching all the documents from collection, we can fetch selected documents based on a criteria.

Example Collection :

db.employee.find()
    { "_id" : ObjectId("5b3b70096728a1b55ecec85d"), "Employeeid" : 5, "dept_id" : 3, "EmployeeName" : "Mahesh", "location" : [ { "city" : "Chennai", "state" : "Karnataka" } ] }
    { "_id" : ObjectId("5b3b70706728a1b55ecec85e"), "Employeeid" : 1, "dept_id" : 2, "EmployeeName" : "Mohan", "location" : [ { "city" : "Trichy", "state" : "TN" } ] }
    { "_id" : ObjectId("5b3b70706728a1b55ecec85f"), "Employeeid" : 2, "dept_id" : 2, "EmployeeName" : "James", "location" : [ { "city" : "Chennai", "state" : "TN" } ] }

1.Equality Criteria:

For example: I want to fetch the data of “Mohan” from ’employee’ collection. The command for this should be:

db.employee.find({EmployeeName : “Mohan”}).pretty()

This command returns the document matching the given criteria.

    {
            "_id" : ObjectId("5b3b70706728a1b55ecec85e"),
            "Employeeid" : 1,
            "dept_id" : 2,
            "EmployeeName" : "Mohan",
            "location" : [
                    {
                            "city" : "Trichy",
                            "state" : "TN"
                    }
            ]
    }

2.Greater Than Criteria:

Syntax:

db.collection_name.find({“field_name”:{$gt:criteria_value}}).pretty()

For example: I would like to fetch the details of ’employee’ having dept_id > 2 then the query should be:

db.employee.find({“dept_id”:{$gt:2}}).pretty()

db.employee.find({"dept_id":{$gt:2}}).pretty()
    {
            "_id" : ObjectId("5b3b70096728a1b55ecec85d"),
            "Employeeid" : 5,
            "dept_id" : 3,
            "EmployeeName" : "Mahesh",
            "location" : [
                    {
                            "city" : "Chennai",
                            "state" : "Karnataka"
                    }
            ]
    }

3.Less than Criteria:

Syntax

db.collection_name.find({“field_name”:{$lt:criteria_value}}).pretty()

Example: Find all the employee having dept_id less than 3. The command for this criteria would be:

> db.employee.find({"dept_id":{$lt:3}}).pretty()
    {
            "_id" : ObjectId("5b3b70706728a1b55ecec85e"),
            "Employeeid" : 1,
            "dept_id" : 2,
            "EmployeeName" : "Mohan",
            "location" : [
                    {
                            "city" : "Trichy",
                            "state" : "TN"
                    }
            ]
    }
    {
            "_id" : ObjectId("5b3b70706728a1b55ecec85f"),
            "Employeeid" : 2,
            "dept_id" : 2,
            "EmployeeName" : "James",
            "location" : [
                    {
                            "city" : "Chennai",
                            "state" : "TN"
                    }
            ]
    }

4. Not Equals Criteria:

Syntax:

db.collection_name.find({“field_name”:{$ne:criteria_value}}).pretty()

Example: Find all the ’employee’ where dept_id is not equal to 2. The command for this criteria would be:

db.employee.find({“dept_id”:{$ne:2}}).pretty()

db.employee.find({"dept_id":{$ne:2}}).pretty()
    {
            "_id" : ObjectId("5b3b70096728a1b55ecec85d"),
            "Employeeid" : 5,
            "dept_id" : 3,
            "EmployeeName" : "Mahesh",
            "location" : [
                    {
                            "city" : "Chennai",
                            "state" : "Karnataka"
                    }
            ]
    }

The other two criteria:

Greater than equals Criteria:

db.collection_name.find({"field_name":{$gte:criteria_value}}).pretty()

Less than equals Criteria:

db.collection_name.find({"field_name":{$lte:criteria_value}}).pretty()