08 - Databases

Question 1

reasons for application processes to stop (3)

Answer 1

1. hardware/software failure
2. need to upgrade or replace hardware
3. need to update software

Question 2

data can be stored in two types

Answer 2

1. flat files (txt, csv, binary)
2. databases (sql, nosql, relational, document-based)

Question 3

an open-source document-based database (NoSQL)

Answer 3

mongodb

Question 4

mongodb features (3)

Answer 4

1. high performance
2. high availability
3. easy scalability

Question 5

an alternative to Relational Database Management Systems in Web Applications

Answer 5

NoSQL DBs

Question 6

schema-less collections are good for _____ data

Answer 6

semi-structured data

Question 7

mongodb works with what type of data storage?

Answer 7

documents in collections

Question 8

serves as the container for collections

Answer 8

database

Question 9

contain documents and are schema-less

Answer 9

collections

Question 10

true/false

several documents within the same collection can only contain the same set of fields

example:

a user can have a first name, middle name and last name, all other users must have all of the fields filled out (first name, middle name, last name)

Answer 10

false, it can be of different sets of fields

Question 11

true/false

mongodb automatically assignes a primary key for new documents called _key

Answer 11

false, the primary key is labelled as _id

Question 12

which version/s of mongodb is a version key generated for new documents

Answer 12

in version3+

Question 13

the version key is incremented after the execution of which functions (2)

Answer 13

save or findOneAndUpdate

basically every update in the document

Question 14

data relationships are supported using (2) types of documents

Answer 14

1. embedded documents
2. referenced documents

Question 15

mongodb commands are centered around ____

Answer 15

queries in the form of documents/JSON

Question 16

syntax for find command

Answer 16

db.<collectionName>.find(<query>)
db['collectionName'].find(<query>)

Question 17

syntax for update command

Answer 17

db.<collectionName>.find(
     <query>,
     <update>,
     <options>
)

Question 18

syntax for remove command

Answer 18

db.<collectionName>.remove(<query>)

Question 19

what type of document is this

{
    code: "CMSC100",
    students: 17,
    sections: [
            {section : "EF-1L"},
            {section : "EF-2L"}
    ]
}

Answer 19

embedded document, the section documents are embedded in the subject document

Question 20

advantage of using embedded documents

Answer 20

keeping related data in a single document makes it easy to query and update

Question 21

disadvantage of using embedded documents

Answer 21

extremely large embedded documents can impact read/write performance

Question 22

what type of document is this

{
    code: "CMSC100",
    students: 17,
    sections: [
            ObjectId("123456"),
            ObjectId("7891011")
    ]
}

Answer 22

referenced documents, the section documents are referenced inside a subject document through their object ids

Question 23

advantages of using referenced documents (2)

Answer 23

1. multiple documents can refer to the same external document
2. avoids the pitfalls of excessively large embedded documents

Question 24

disadvantage of using referenced documents

Answer 24

requires additional querying that many developers want to avoid

Question 25

support for embedded documents reduces need for joins and multi-document queries on the database

Answer 25

high performance

Question 26

mongodb supports replica sets which provide redundancy

Answer 26

high availability

Question 27

how does replica sets reduce downtime to nearly zero

Answer 27

mongodb supports replica sets, meaning a set or copy of the database is always available even when the administrator is pushing updates

Question 28

mongodb supports sharding

Answer 28

scalability

Question 29

what does sharding mean?

Answer 29

distribution of data across several machines

Question 30

give the NoSQL term equivalent of the following: a. Database b. Table c. Row d. Column e. Table Join f. Primary Key

Answer 30

a. Database b. Collection c. Document d. Field e. Embedded Document f. Primary Key

Question 31

true/false there is no need for you to convert data stored in databases to a data structure in order to use it

Answer 31

false, you need to convert it to a data structure your PL can understand

Question 32

the process of converting data between systems of incompatible data types, using object-oriented methods

Answer 32

Object Relational Mapping

Question 33

provides an object-oriented way to access and manipulate the data in our DBs

Answer 33

object relational mapping/object document mapping

Question 34

equivalent NoSQL term of object relational mapping

Answer 34

object document mapping

Question 35

advantages of using orm (3)

Answer 35

1. in-depth knowledge of the DB is not required for application development 2. DB querying optimization is independent from business logic 3. underlying DB technology can easily be changed