database system
TRANSCRIPT
Has everyone noticed that all letters of the word database are typed with left hand? Now the layout of the QWERTY typewriter keyboard was designed, among other things, to facilitate the even use of both hands. It follows, therefore, that writing about databases is not only unnatural, but a lot harder than it appears.
Tight control of data redundancy. Enforces user-defined rules to ensure the integrity of table data. Has a centralized data dictionary for the storage of information pertaining to data and its manipulation. Ensures that the data can be shared across applications. Enforces data access authorization. Has automatic, intelligent backup and recovery procedure for data. Have different interfaces via which users can manipulate data.
Data redundancy and inconsistency
Difficulty in accessing data
Data isolation
Integrity problems
Atomicity problems
Concurrent-access anomalies
Security problems
Data Abstraction
Instances and Schemas
Data Independence
External Schema 1
External Schema 2
External Schema 3
Conceptual Schema
Physical Schema
Disk
Levels of Abstract ion in DBMS
sidsid namename loginlogin ageage gpagpa
53665366 JonesJones jones@csjones@cs 1818 3.43.4
53685368 SmithSmith smith@eesmith@ee 1818 3.23.2
53655365 GulduGuldu guldu@musicguldu@music 1212 2.02.0
Students (sid: string, name: string, login: string, age: integer, gpa: real)
An Instance of the Students Relation
Logical Data Independence
Physical Data Independence
Object-Based Logical Models
Social-security
Customer-name
Customer-street
Customer-city Account-number
balance
customer accountdepositor
A Sample E-R Diagram
Record-Based Logical Models The entity-relationship model
The object-oriented model
Relational Model
Network Model
Hierarchical Model
Record-Based Logical Models
customer-name social-security customer-street customer-city account-number
Jhonson 912-83-7465 Alma Palo Alto A-101
Smith 019-28-3746 North Rye A-215
Hayes 677-89-9011 Main Harrison A-102
account-number
balance
A-101 500
A-215 700
A-102 400
Jhonson
192-83-7465 Palo AltoAlma
Smith
Hayes
Lindsay
Turner
Jones
091-28-3746
677-89-9011
182-73-6091
321-12-3123
336-66-9999
North
Main
Putnam
Main
Park
Rye
Harrison
Stamford
Harrison
Pittsfield
A-101
A-222
A-215
A-102
A-305
A-201
A-217
500
700
400
350
900
750
700
A Sample Network Database
Jhonson 192-83-7465 …
Smith
Hayes
Lindsay
Turner
Jones
091-28-3746
677-89-9011
182-73-6091
321-12-3123
336-66-9999
…
…
…
…
…
A-101 A-222
A-215
A-102
A-305
A-201
A-217
500
700
400
350
900
750
700
A-201 900
A Sample of Hierarchical Database
Naive Users
Online Users
Application Programmers
Database Administrator
Design of the conceptual and physical schemas
Security and authorization
Data availability and recovery from failures
Integrity-constraint specification
Database tuning
Data Definition Language
Data Manipulation Language
Naïve users(tellers, agents,
etc.)
Application programmers
Sophisticated users
Database administrator
Application interface Application programs
Query Database scheme
indices Statistical data
Data dict ionaryData fi les
Application programs
object code
Embedded DML
precompiler
Query evaluation
engine
DML compiler
DDL interpreter
Transaction manager
Buffer manager
File manager
users
disk storage
Data base
management
system
query processor
storage manager
System Structure
Database procedure calls Precompiler
Modif ied application
program
HLL compiler
Application program
Compiled & optimized
versionLink editor Object module
Binary version of application program
OS & fi le subsystem
DBMS & data manager
Run-time system
Main memory
Processing Database Applicat ion in High-Level Language
DatabaseDBMS-user inter-
faceData
managerFile
managerDisk
manager
Response to user
Requested record
Requested block(s)
Block(s) from secondary storage
User’s query
Request specific record
Request specific block(s) Input/output
block(s)
Steps in Data Access
Reduction of redundancies
Shared data
Integrity
Security
Conflict resolution
Data independence
Problems associated with centralization
Cost of software/hardware and migration
Complexity of backup and recovery
