Exam 1.1 Flashcards
(29 cards)
Flat File
-Data stored in two dimensional database with no relational info to other files or database info
-often stored as CSV
Declarative language
focusses on defining the result rather than steps to get there
imperative langauge
Explicitly states the steps needed to achieve a goal
What language do DBMS use
Declarative (SQL)
Relational Data Model
The way of storing data in tables which are just realtions
schema
structure that describes how data is stored in tables
External Schema
Describes how users see data
Conceptual/Logical Schema
describes the logiccal structure of DBMS
Physical Schema
The files and indices used
what langauge is data defined in
DDL
what language is data modified
DML
Physical Data Independence
Protection from physical changes in data
Logical Data independence
Protection from changes in logic structre of data
ER diagram
Entity relation diagram describes data as set of entities and relationships
what does an entity, relationship and attribute look like in er diagram
entity: rectangle
relationship: diamond
attrivute: oval
Key constraints
define how many relations an entity can have with another
Participation Constraint
There is at least 1
How to interpret key constraint
Where arrow is on denotes which can have one
How to interpret participation constraint
where bold line denotes which must be involved in relation
Key
a minimal set of attributes unique for each record
Candidate key
potential key and shares the same properties with it
Primary Key
-Main candidate key
-Underlined in ER diagram
Relationship set
set of relatonships other entities have with eachother
True of False only entities can have attributes
False relationships can have it too
