Untested Chapter Notes

Question 1

CAP theory

Answer 1

Consistency
* All replicas contain the same version of data
* Client always has the same view of the data(no matter what node)

Availability
* System remains operational on failing nodes
* All clients can always read and write

Partition tolerance
* Partition tolerance means that entire clusters can still work even if a network
partition causes communication interruption between nodes.
* System remains operational on system split(communication malfunction)
* System works well across physical network partitions

Question 2

What is Oracle RAC

Answer 2

Oracle Real Application Clusters (RAC) allow
customers to run a single Oracle Database across
multiple servers to maximize availability and enable
horizontal scalability, while accessing shared storage.

Question 3

Sharding

Answer 3

Uses range-based partitioning to distribute documents based on a
specific shard key
* Shard key: a single indexed field for now

Question 4

How does NoSQL differ from RDBMS?

Answer 4

• Looser schema definition
• Designed to handle distributed, large databases
• Query language through the API
• Relaxation of the ACID (Atomicity, Consistency, Isolation, Durability)
  properties

Question 5

SQL Database is horizontally scalable while NOSQL is vertically scalable T/F

Answer 5

False

Question 6

Benefits of NoSQL

Answer 6

• Elastic Scaling
• DBA Specialists
• Big Data
• Flexible data models
• Economics:
  - No SQL: clusters of cheap commodity servers to manage the data and transaction volumes
  
  • Cost per gigabyte or transaction/second for NoSQL can be lower than the cost for a RDBMS

Question 7

Drawbacks of NoSQL

Answer 7

• Support: New open source projects with startup support; no reputation
• Maturity: still implementing their basic feature set
• Administration: no administrator necessary however NoSQL still requires effort to maintain
• Lack of Expertise
• Analytics and Business Intelligence

Question 8

MongoDB

Answer 8

Developed in C++ by 10gen founded in 2007
NoSQL database
* Hash-based, schema-less database
* No Data Definition Language
* Uses BSON format: Binary of JSON
* Supports APIs (drivers) in JavaScript, Python, Ruby, Perl, Java, C#, C++.

Question 9

JSON

Answer 9

JavaScript Object Notation – language independent
* JSON is a lightweight format for storing and transporting data.

Question 10

JSON Data types

Answer 10

a string, a number, an object (JSON object), an array, a boolean, a null

Question 11

BSON

Answer 11

a binary-encoded serialization of JSON-like documents.

Question 12

Advantages of MongoDB

Answer 12

Speed, Sharding, Flexible Database, Horizontal Scalability

Question 13

Disadvantages of MongoDB

Answer 13

Joins not supported, limited data size

Question 14

Applications of MongoDB

Answer 14

• Web Content Management
• Real-Time Analytics
• Internet of Things (IoT)

Question 15

Is MongoDB ACID compliant?

Answer 15

No

Question 16

JSON data type cannot be a function, a date, undefined T/F

Answer 16

True

Question 17

JSON Data Structures

Answer 17

Object: Collection of name-value pairs
Array: List of values

Question 18

JSON Syntax

Answer 18

Begins with { (left brace) and Ends with }(right brace)
* Each name is followed by :(colon)
* Name/value pairs are separated by ,(comma)
* Square brackets hold arrays

Question 19

BSON – Basic types

Answer 19

Basic types:
* byte 1 byte (8-bits)
* int32 4 bytes (32-bit signed integer, two’s complement)
* int64 8 bytes (64-bit signed integer, two’s complement)
* uint64 8 bytes (64-bit unsigned integer)
* double 8 bytes (64-bit IEEE 754-2008 binary floating point)
* decimal128 16 bytes (128-bit IEEE 754-2008 decimal floating
point)

Question 20

BSON - Element - Structure - Type Selector

Answer 20

• 0x01 = double
• 0x10 = 4byte integer
• 0x12 = 8byte integer
• 0x08 = boolean
• 0x0A = null
• 0x09 = datetime
• 0x11 = timestamp

Question 21

Collection and Documents MongoDB

Answer 21

Collection
* Collection of documents, usually of a similar structure
* Document
* MongoDB document = one JSON object (BSON)
* Each document has a unique idenƟfier (primary key)
* – Technically realized using a top-level _id field

Question 22

MongoDB: Object Hierarchy

Answer 22

A MongoDB database may have one or
more ‘collections’.
* A collection may have zero or more
‘documents’.
* A document may have one or more
‘fields’.

Question 23

MongoDB documents are not internally stored in BSON format and the maximum allowed size is 15 mb (t/f)

Answer 23

False

Question 24

Semi-structured model

Answer 24

is a database model where there is no
separation between the data and the schema

Question 25

Mongod (Astaghfirullah)

Answer 25

is the primary daemon process of MongoDB system. It handles data
requests, manages data access, and performs management operations.

Question 26

You can have multiple mongos for the system (T/F)

Answer 26

False, you can have one mongo for the whole system no matter how many mongods.

You also can have one local mongos for every client if you wanted to
minimize network latency.

Question 27

CRUD Operations

Answer 27

Create, read, update, delete; No data definition language (DDL) in MongoDB.
MongoDB is schemeless.

Question 28

MongoDB read operations

Answer 28

find(): primary method to select documents from a collection
* It is identical to “select * from table_name;”
* findOne(): returns only a single object

Question 29

MongoDB update operations

Answer 29

update(): corresponds to the UPDATE operation in SQL
* updateOne()
* Updating values uses the $set operator.

Question 30

MongoDB insert

Answer 30

Insert(): similar to SQL insert command
* save(): performs the same as insert()
* insertOne()
* insertMany()

Question 31

MongoDB delete

Answer 31

Remove(): similar to SQL delete
* deleteOne()
* deleteMany()
* Note: it seems that MongoDB does not have delete() function

Question 32

What does $unset do

Answer 32

deletes a particular field