JavaScript Set 9

Question 1

What does BSON stand for an what is it?

Answer 1

Stands for Binary JavaScript Object Notation (Binary JSON). It is a binary-encoded serialization format to represent data. Data in MongoDB is stored in BSON format for efficient storage and fast operations

Question 2

What does it mean that MongoDB is schemaless?

Answer 2

Don’t need to configure database columns with types
No data definition language is required

Question 3

What is the hierarchy of items in MongoDB

Answer 3

A MongoDB instance can have zero or more databases
A database can have zero or more collections
A collection can have zero or more documents
A document can have one or more fields

Question 4

What are some facts about MongoDB documents?

Answer 4

1. Documents in the same collection don’t have to have the same fields
2. Documents are the same as records in RDBMS
3. Documents can embed other documents
4. Documents are addressed in the database with a unique key

Question 5

How much faster is MongoDB than MySQL?

Answer 5

Anywhere from 2 to 10 times faster

Question 6

What is indexing?

Answer 6

A data structure technique that allows users to quickly retrieve records from a database file. It optimizes database performance by minimizing the number of queries

Question 7

What is an index?

Answer 7

A small table with only two columns. The first column is a copy of the primary key of a table, the second is a set of pointers that points to the address where data is saved

Question 8

How are indexes in MongoDB defined and supported?

Answer 8

They are defined on a per collection level
They are supported on any field or sub-field within a document

Question 9

What is sharding?

Answer 9

Distributing data across multiple servers to achieve horizontal scalability

Question 10

What is a mongod?

Answer 10

A database instance

Question 11

What are mongos?

Answer 11

Sharding processes. Analogous to a database router, processes all requests, decides how many and which mongods should receive the query, collates results, and sends it back to the client

Question 12

What is mongo?

Answer 12

An interactive shell. Fully functional JavaScript environment for use with MongoDB

Question 13

How many mongos do you need for a system?

Answer 13

You can have one mongos for the whole system no matter how many mongods you have. Or, you can have one local mongos for every client to minimize network latency

Question 14

What are the limitations of MongoDB?

Answer 14

1. No referential integrity
2. Updating something in many places instead of one because of horizontal scalability
3. Lack of a predefined schema meaning objects in a collection can be completely inconsisten

Question 15

What does having no referential integrity mean?

Answer 15

Referential integrity is the relationship between tables which is managed in RDBMS by primary and foreign keys. MongoDB does not have this

Question 16

How do you start and connect to mongo?

Answer 16

1. Create an empty folder to contain the database files
2. Start the mongo server
   mongod.exe –dbpath c:\data\db (or other path)
3. In a separate terminal, run the mongo client shell to access the database
   mongo.exe