Data Science

The Three V's of Big Data

• Volume: number of rows/objects/bytes
• Variety: number of columns/dimensions/sources
• Velocity: number of rows/bytes per unit time

(Veracity: Can we trust this data?)

Data Model

Three components:

• Structures
• Constraints
• Operations

What is a database? A collection of information organized to afford efficient retrieval.

Why do we need a database?

• Sharing
• Data model enforcement
• Scale
• Flexibility

Relational Algebra

http://en.wikipedia.org/wiki/Relational_algebra

Operations

• Union $\cup$, intersection $\cap$, difference $-$
• Selection $\sigma$
• Projection $\Pi$
• Join $\bowtie$
• (Extended RA) Duplicate elimination $d$
• (Extended RA) Grouping and aggregation $g$
• (Extended RA) Sorting $t$

Join

• Equi-join $\bowtie_{A=B}$
• $\theta$-join $\bowtie_\theta$