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

Operations

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