Difference between revisions of "Data Science"
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=== Relational Algebra === | === Relational Algebra === | ||
| + | http://en.wikipedia.org/wiki/Relational_algebra | ||
| + | |||
Operations | Operations | ||
* Union $\cup$, intersection $\cap$, difference $-$ | * Union $\cup$, intersection $\cap$, difference $-$ | ||
Latest revision as of 22:50, 2 September 2013
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 $\bowtie_\theta$