NoSQL

Question 1

What are some examples of common set of features use on NoSQL Databases:

Answer 1

❑ Non-relational data model.
❑ Runs well on clusters.
❑ Mostly open-source.
❑ Built for the new generation Web applications.
❑ Is schema-less.

Question 2

What is ACID?

Answer 2

Atomicity
Consistency
Isolation
Durability

Question 3

What are the 4 basic types of NOSQL?

Answer 3

1) Key-Value (hash table of keys. E.G.)
2) Document-based (comprise of documents with tagged elements. E.G.: MongoDB)
3) Column-based (each block contains data from only one column E.G.: HBase, Cassandra)
4) Graph-based (used nodes for storage. E.G.: InfiniteGraph, FlockDB)

Question 4

What is the CAP Theorem?

Answer 4

CAP theorem is also called brewer’s theorem. It states that is impossible for a distributed data store to offer more than two out of three guarantees.
❑ Consistency: The data should remain consistent even after the execution of an operation. This means once data is written, any future read request should contain that data. For example, after updating the order status, all the clients should be able to see the same data.
❑ Availability: The database should always be available and responsive. It should not have any downtime.
❑ Partition Tolerance: Partition Tolerance means that the system should continue to function even if the communication among the servers is not stable.

Question 5

What is BASE?

Answer 5

• Basically available
• Soft State
• Eventually consistent

Question 6

What is the RDBMS database

Answer 6

❑ Data is stored in a relational model, with rows and columns.
❑ A row contains information about an item while columns contain specific information, such as ‘Model’, ‘Date of Manufacture’, ‘Color’.
❑ Follows fixed schema. Meaning, the columns are defined and locked before data entry. In addition, each row contains data for each column.
❑ Supports vertical scaling. Scaling an RDBMS across multiple servers is a challenging and time-consuming process.
❑ Atomicity, Consistency, Isolation & Durability(ACID) Compliant

Question 7

What are the characteristics of NoSQL?

Answer 7

❑ Data is stored in a host of different databases, with different data storage models.
❑ Follows dynamic schemas. Meaning, you can add columns anytime.
❑ Supports horizontal scaling. You can scale across multiple servers. Multiple servers are cheap commodity hardware or cloud instances, which make scaling cost-effective compared to vertical scaling.
❑ Not ACID Compliant.

Question 8

What is the column based NoSQL?

Answer 8

❑ Column-based databases store data in column families as rows. These rows contain multiple columns associated with a row key.
❑ Column families are groups of related data that is accessed together.

For example, you may access customer profile information at the same time, but not their
order history.
➢ Each column family is like a container of rows in an RDBMS table where the key identifies the rows.
➢ Each row consists of multiple columns. However, the various rows need not have the same columns. Moreover, you can add a column to any row at any time without adding it to other rows.