Relational Database & ER Diagram Flashcards
Intro, relational databases, and er diagrams
Ubiquitous computing
computers/sensors that are everywhere
RDBMS
Relational Database Management System
SQL
Structured Query Language, a programming language for interfacing with a relational database
Schema
how data is represented
Internal Schema
comprised of logical and physical schemas
Conceptual schema
comprehensive design of our database (ex: ER diagrams, documentation, views)
External Schema
how data is viewed by end users
ER Diagram
Entity-relationship diagram, graphical notation for communicating the design of a database
Entity types
very similar to classes, represent with a box
Attributes
describe properties of an entity, represent with an oval
Set-valued attribute
contains > 1 value, multi-value, represent with double oval (ex: skills)
Composite attributes
attribute divided into smaller pieces, represent as a hierarchy of ovals (ex: date or name)
Optional attributes
optional fields, represent with an oval with an asterisk or italicized text
Derived attributes
not stored, but can be calculated, represent with a dashed oval
Keys
make an entity unique, represent with an underline
Composite key
two or more attributes needed for a unique entry
Relationships
connect two tables together, can be 1:1, 1:many, or many:many, represent with a diamond
Foreign key
primary key from another entity type, represent with a dotted underline
Weak entity type
relies on the existence of other entities, represent with a double outline for both entity and relationship
Tuple
row in a relational database, one entry
Attribute
column in a relational database
