Transcript Database

Databases and Database Users
Outline: Introduction
(Chapter 1 – 3rd , 4th , 5th, 6th ed.)
• What is a database?
• The main characters of a database system
• The basic database design method
• The entity-relationship data model for application
modeling
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Databases and Database Users
Types of databases
• traditional
• multimedia - pictures, video, sound
• Scientific database
- GIS: maps, weather, satellite images
- biological database: DNA sequence analysis
• warehouse, OLAP - analysis, decision making
• real-time, active databases - industrial processes
• deductive databases - combination of inference and
databases
• web databases
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Databases and Database Users
Types of databases
• traditional
• multimedia - pictures, video, sound
• GIS - maps, weather, satellite images
• data warehouse, OLAP - analysis, decision making
• real-time, active databases - industrial processes
• deductive databases - combination of inference and
databases
Read Chapter 1
• web databases
For next day, read Chapters 2 and 3
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Databases and Database Users
Database
• collection of related data
• represents some aspect of the real world
• logically coherent collection
• built with a specific purpose in mind
• could be anywhere - notebook, spreadsheet, Access,
Oracle, … could be manual / could be computerized
Data
• known and recordable facts
• name, phone number, address, grade, ...
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Databases and Database Users
Database Management System (DBMS)
• collection of software facilitating the definition,
construction and manipulation of databases
Definition
•record structure
•data elements
•names
•data types
•constraints
etc
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Construction
•create database
files
•populate the
database with
records
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Manipulation
•querying
•updating
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Databases and Database Users
Database Management System (DBMS)
• collection of software facilitating the definition,
construction and manipulation of databases
DBMS
Meta data
Request
manager
Storage
manager
Stored
database
Users/
actors
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Databases and Database Users
Sample database
file2
file1
Course CName CNo CrHrs Dept
Database 8803 3
CS
C
2606 3
CS
Student Name StNo Class Major
Smith 17
1
CS
Brown
8
2
CS
Grades StNo Sid Grade
17
25 A
17
43 B
Section SId CNo Semester Yr
Instructor
32 8803 Spring 2000 Smith
25 8803 Winter 2000 Smith
43
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2606
Spring 2000 Jones
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file4
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Databases and Database Users
Meta data for table structures
REL_NAME ATTR_NAME ATTR_TYPE MEMBER_OF_PK MEMBER_OF_FK FK_RELATION
Cname
VSTR15
no
no
Course
Dept
STR9
no
no
Student
Name
STR20
no
no
Student
StNo
INTEGER
yes
no
StNo
INTEGER
no
yes
Course
... ...
... ...
Grade
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Student
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Databases and Database Users
Characteristics of the Database approach
• single repository of data
• sharable by multiple users
•concurrency control
•transaction control
• self-describing - system catalogue contains meta data
• program-data independence
• some changes to the database are transparent to
programs/users
• multiple views of data - to support individual needs of
programs/users
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Databases and Database Users
Database Actors
• Database Administrator (DBA)
-
authorizing access to the database
coordinating and monitoring its use
aquiring software and hardware as needed
solving problems such as breach of security or poor system
performance
• Database Designers/Modelers
-
identifying the data to be stored
choosing appropriate data structure
• End-users
-
access to the database: querying, updating, generating reports
• Software Engineers
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developing application programs
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Databases and Database Users
Advantages of the Database approach
(capabilities we would look for in a DBMS)
• controlled redundancy
• database design integrates different user data needs
• performance tuning may lead to replicated data
• controlled/authorized access to data
• SQL Grant and Revoke commands
• enforcing integrity constraints
• intra-record constraints: e.g. data type, net<gross
• inter-record constraints: StNo in “Grades” exists as a
StNo in “Student”
• backup and recovery
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Databases and Database Users
Implications of the Database approach
• standards enforcement
• DBA can enforce standard naming conventions, etc
• reduced application development time
• adding new functionality to an existing database is
“easy”
• flexibility
• adding new data and making some types of changes is
“easy”
• up-to-date information - due to sharable characteristic
• economies of scale - due to sharable resources the whole
organization can make one investment
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Databases and Database Users
When not to use a DBMS
• overhead costs are too great
• high initial investment
• generality
• overhead of security, concurrency control, recovery,
integrity
• data and applications are simple, well-defined, not expected to
change
• stringent real-time constraints
• multi-user environment not needed
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Databases and Database Users
Database design
• let’s jump ahead to see this
• ERDs are covered in Chapter 3
Course
1
Student
Delivery
M
N
Grades
Section
N
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Databases and Database Users
Database design
• let’s jump ahead to see this
• ERDs are covered in Chapter 3
Course
StNo
Class
1
Student
Major
Delivery
Name
M
N
Grades
Section
N
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Databases and Database Users
Database design
• let’s jump ahead to see this
• ERDs are covered in Chapter 3
CNo
CrHrs
Dept
Course
StNo
Class
CName
1
Student
Major
Delivery
Name
M
N
Grades
Section
N
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Databases and Database Users
Database design
• let’s jump ahead to see this
CNo
CrHrs
• ERDs are covered in Chapter 3
Dept
Course
StNo
Class
CName
1
Student
Major
Delivery
Name
M
N
Grades
Semester
Section
N
Year
SId
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Instructor
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Databases and Database Users
Database design
• let’s jump ahead to see this
CNo
CrHrs
• ERDs are covered in Chapter 3
Dept
Course
StNo
Class
CName
1
Student
Major
Delivery
Name
M
N
Grades
Semester
Section
N
Year
grade
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SId
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Instructor
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name number
With attributes, etc:
fname
name
ssn
bdate
degree
1
lname
minit
sex
address
employee
supervisor
department
works for
N
salary
1
startdate
1
location
1
controls
manages
1
N hours
N
supervisee
number of
employees
N
M
1
works on
supervision
dependents of
project
name number
location
N
dependent
name
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sex
birthdate relationship
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ER-to-Relational mapping
1. Create a relation for each strong entity type
2. Create a relation for each weak entity type
• include primary key of owner (an FK - foreign key)
• owner’s PK + partial key becomes PK
3. For each binary 1:1 relationship choose an entity and
include the other’s PK in it as an FK. Include any
attributes of the relationship
4. For each binary 1:n relationship, choose the n-side entity
and include an FK w.r.t the other entity. Include any
attributes of the relationship
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5. For each binary M:N relationship, create a relation for the
relationship
• include PKs of both participating entities and any
attributes of the relationship
• PK is the concatenation of the participating entity PKs
6. For each multivalued attribute create a new relation
• include the PK attributes of the entity type
• PK is the PK of the entity type and the multivalued
attribute
7. For each n-ary relationship, create a relation for the
relationship
• include PKs of all participating entities and any attributes
of the relationship
• PK may be the concatenation of the participating entity
PKs
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