MongoDB

Question 1

The base of traditional relational database management systems:

Answer 1

Atomicity: All operations in a transactionsucceeds or rolled back.

Consistency: After a transaction completed, the database remains consistence.

Isolation: Transactions are executed without interfering with other transactions.

Durability: After a transaction completed, changes will be permanent.

Question 2

Define NoSQL

Answer 2

No SQL is a generic term that refers to any non-relational data management system and does not use SQL query language.

Question 3

MongoDB features:

Answer 3

Indexing
Aggregations
File Storage
Special collection types

Question 4

Create a collection named “newCollection” and insert the field “field” and the value “value :

Answer 4

> db.newCollection.insertOne({“field” : “value”})

Question 5

Create a database named “myNewDb”

Answer 5

> use myNewDb

Question 6

Drop the current database

Answer 6

db.dropDatabase()

Question 7

Add one document to the collection “TestKey” with an id of 1 and a name of “test2”

Answer 7

db.TestKey.insertOne({_id:1, Name: “test2”})

Question 8

The command to insert multiple documents into a collection:

Answer 8

db.collection.insertMany([
{ // fields and values } ,
{ // fields and values }
])

Question 9

display the “Employee” collection

Answer 9

db.Employee.find()
OR
db.Employee.find().pretty()

Question 10

display all databases

Answer 10

show dbs

Question 11

display collections of current database

Answer 11

show collections

Question 12

show all the collections in an array:

Answer 12

db.getCollectionNames()

Question 13

drop the collection “Dept”

Answer 13

db.Dept.drop()

Question 14

create a collection named “Room”

Answer 14

db.createCollection(“Room”)

Question 15

Remove all documents in the collection “foo”

Answer 15

db.foo.remove()

Question 16

remove all documents from the mailing.list collection where the value “opt-out” equals “true”

Answer 16

db.mailing.list.remove({“opt-out” : true })

Question 17

Delete Documents for one and for many

Answer 17

db. collection.deleteOne({//fields and values})

db. collection.deleteMany()

Question 18

Update the documents in the collection “Course” that have the “NumOfHours” value as 48. Change the CourseName to “OOP 1”

Answer 18

db.Course.updateOne(
{NumOfHours : 48},
{$set : {CourseName : “OOP 1”}}
)

Question 19

Update multiple documents from the collection “Course” where NumOfHours is 48 and Program.Duration is 3 years. Set the CourseName to “System Design”

Answer 19

db.Course.updateMany(
{ $and : [ {NumOfHours: 48},
{Program.Duration : “3 years”} ] },
{$set : {CourseName: “System Design”}} )

Question 20

What are the comparison operators for :
<
<=
>
>=
!=

Answer 20

$lt
$lte
$gt
$gte
$ne

Question 21

Query employees who are between the ages of 25 and 40

Answer 21

db.Employee.find({age: {$gte: 25, $lte 40 }})

Question 22

Find the employees details who are earning less or equal to 2000

Answer 22

db.Employee.find({salary: {$lte : 2000}})

Question 23

Find all employees details who are not working HR department.

Answer 23

db.Employee.find({department: {$ne : “HR”}})

Question 24

find employees with a salary of either 1200, 2000, or 2500

Answer 24

db.Employee.find({salary: {$in : [1200, 2000, 2500] }})

Question 25

find employees that DON’T have a salary of either 1200, 2000, or 2500

Answer 25

db.Employee.find({salary: {$nin : [1200, 2000, 2500]}})

Question 26

Display the name of employees where the department name is not HR and the age is 55

Answer 26

db.Employee.find({department.name: {$ne : “HR”}, age: 55}, {name: 1})