Database Systems Exam 1

Traditional Database Applications

banks, reservations, buying things online or retail

Database size limits, maintenance requirements

they can be any size/complexity and take few people to maintain

Database definition

a collection of related data

Data definition

known facts that can be recorded and have an implicit meaning

functions facilitated by DBMS

Define

Construct

Manipulate

Share

Define

defining data types, structures, constraints etc

Construct

loading/inputting initial database information

Manipulate

retieving, modifying, accessing data

Share

multiple people/apps can work on/view db at one

Database System

dbms + Database

order of interaction

user to app

app to dbms

dbms to database/data

querying

retieves data

updating

changes data

DB vs file system

db is self descibing, insulation btwn apps and data, support for multiple viewers/managers

Meta data

the rules governing the structure of a database

Admins

manage db access and use, purchase soft and hardware

Designer

define the db’s content, structure, etc

end users

benefit from the db functions

System Analusts

explains end user to designer vice versa

Advantages of DBMS

single file makes updates easy (controlling redundancy)

restrict data access

efficient storage

backup/recovery

adapt to different users

complex relationships represented

Costs of DBMS

hardware, software, training

defining, processing data

security, concurrency control, recovery, integrety

all these cost money

when not to use DBMS

simple, static dataset

single user

no need for real time

2 parts of database design

data requirements

functional requirements

data requirements

what info must be heldf

functional requirements

what must be possible with the data

concept design

step 2 of process

ER model

use to explain database to a client

composite attribute

made of many parts

complex attribute

both composite and multivalued

multivalue attribute

can have multiple values

ex many phone numbers

Cardinality

1:N, M:N, etc

partial key

the set of atributes that can uniquely identify weak entities that are related to the same owner entity

semantics

added by EER

sub/supergroups

inheritance, specialization generalization

specialization

top down

defining subclasses for your superclass

generalization

bottom up

defining superclasses for your subclasses

Spec and Gen constraints available

completeness

disjointness

completeness

double line

you MUST be a member of one of these subclasses

disjointness

little d in the circle

you can only choose one

overlapping

little o in the circle

you can be many

hierarchy

every subclass has one superclass

lattice

there is at least one instance of a subclass with more than one superclass

shared subclass

inherit from multiple superclasses

union

u in a circle

shared subclass but can only inherit from one place