Week 1 L2

Question 1

What are the benefits of the relational database model?

Answer 1

Mature and robust
Supported well by most programming languages
Large knowledge and skill base
Correctness is ensured by ACID

Question 2

What are the problems with relational databases pre defined schema and integrity .

Answer 2

Shared application database- Relational database can serve many applications but all aps must use relational model to access data
Some collection of data simply do not fit well into the relational model
A pre-defined schema is highly structured and becomes difficult to change later
Rules of normalisation are too restrictive and result in too many joins.
Availability and low latency could be more important than absolute integrity

Question 3

What is Object relational impedance mismatch

Answer 3

relational databases don’t match well with OOP

Question 4

Why are Relational databases not good over a cluster ?

Answer 4

Relational database not designed to run over cluster, could cause integrity problems
Join may be needed across multiple nodes of cluster
Traditional machine licenses are too costly

Question 5

What is cluster computing

Answer 5

A set of computers that work together so they can be viewed as a single system

Question 6

What are the benefits of NoSQL ?

Answer 6

Store data in different formats such as XML and JSON. This avoids impedance mismatch
No schema/rules
Take advantage of aggregate data modeling

Question 7

What is aggregate data modeling ?

Answer 7

group a collection of data to act as a unit

Question 8

What are the benefits of aggregate modeling ?

Answer 8

Aggregate(unnormalized) modeling keeps units ofdata on same machine
Aggregate can be aligned to single atomic transaction
Languages built to handle clustering e.g. map reduce programming