Database Systems
Review of Chapters 1-4 & 6
Chapter 1: Database Systems
• The difference between data and information
• What a database is, the various types of databases,
and why they are valuable assets for decision making
• The importance of database design
• How modern databases evolved from file systems
• About flaws in file system data management
• The main components of the database system
• The main functions of a database management system
(DBMS)
Database Systems, 10th Edition
2
Chapter 1 Key Points
• Data are raw facts
• Information is the result of processing data to
reveal its meaning
• Accurate, relevant, and timely information is the
key to good decision making
• Data are usually stored in a database
• DBMS implements a database and manages its
contents
Database Systems, 10th Edition
3
Chapter 1 Key Points (cont'd)
• Metadata is data about data
• Database design defines the database
structure
– Well-designed database facilitates data
management and generates valuable
information
– Poorly designed database leads to bad decision
making and organizational failure
• Databases evolved from manual and
computerized file systems
Database Systems, 10th Edition
4
Chapter 1 Key Points (cont'd)
• In a file system, data stored in independent files
– Each requires its own management program
• Some limitations of file system data
management:
–
–
–
–
–
Requires extensive programming
System administration is complex and difficult
Changing existing structures is difficult
Security features are likely inadequate
Independent files tend to contain redundant data
• Structural and data dependency problems
Database Systems, 10th Edition
5
Chapter 1 Key Points (cont'd)
• Database management systems were
developed to address file system’s inherent
weaknesses
• DBMS present database to end user as single
repository
– Promotes data sharing
– Eliminates islands of information
• DBMS enforces data integrity, eliminates
redundancy, and promotes security
Database Systems, 10th Edition
6
Chapter 2: Data Models
• Data modeling and why data models are important
• The basic data-modeling building blocks
• What business rules are and how they influence
database design
• How the major data models evolved
• About emerging alternative data models and the need
they fulfill
• How data models can be classified by their level of
abstraction
Database Systems, 10th
Edition
Chapter 2 Key Points
• Hierarchical model
– Set of one-to-many (1:M) relationships between
a parent and its children segments
• Network data model
– Uses sets to represent 1:M relationships
between record types
• Relational model
– Current database implementation standard
– ER model is a tool for data modeling
• Complements relational model
Database Systems, 10th
Edition
Chapter 2 Key Points (cont’d)
• Object-oriented data model: object is basic
modeling structure
• Relational model adopted object-oriented
extensions: extended relational data model
(ERDM)
• OO data models depicted using UML
• Data-modeling requirements are a function of
different data views and abstraction levels
– Three abstraction levels: external, conceptual,
and internal
Database Systems, 10th
Edition
Chapter 3: The Relational Database Model
• The relational database model offers a logical
view of data
• The relational model’s basic component:
relations (table)
• Relations are logical constructs composed of
rows (tuples) and columns (attributes)
• Relations are implemented as tables in a
relational DBMS
10
Database Systems, 10th
Edition
Chapter 3 Key Points
• Tables are basic building blocks of a
relational database
• Keys are central to the use of relational tables
• Keys define functional dependencies
–
–
–
–
–
11
Superkey
Candidate key
Primary key
Secondary key
Foreign key
Database Systems, 10th
Edition
Chapter 3 Key Points(cont’d)
• Each table row must have a primary key that
uniquely identifies all attributes
• Tables are linked by common attributes
• The relational model supports relational algebra
functions
– SELECT, PROJECT, JOIN, INTERSECT
UNION, DIFFERENCE, PRODUCT, DIVIDE
• Good design begins by identifying entities,
attributes, and relationships
– 1:1, 1:M, M:N
12
Database Systems, 10th
Edition
Chapter 4: Entity Relationship (ER) Modeling
• The main characteristics of entity relationship
components
• How relationships between entities are defined,
refined, and incorporated into the database
design process
• How ERD components affect database design
and implementation
• That real-world database design often requires
the reconciliation of conflicting goals
13
Database Systems, 10th
Edition
Chapter 4 Key Points
• Entity relationship (ER) model
– Uses ERD to represent conceptual database as
viewed by end user
– ERM’s main components:
• Entities
• Relationships
• Attributes
– Includes connectivity and cardinality notations
14
Database Systems, 10th
Edition
Chapter 4 Key Points(cont’d)
• Connectivities and cardinalities are based on
business rules
• M:N relationship is only valid at conceptual level
– Must be mapped to a set of 1:M relationships
• ERDs may be based on many different ERMs
• UML class diagrams are used to represent the
static data structures in a data model
• Database designers are often forced to make
design compromises
15
Database Systems, 10th
Edition
Chapter 6: Normalization of Database Tables
• What normalization is and what role it plays in
the database design process
• About the normal forms 1NF, 2NF, 3NF (3 of 5)
• How normal forms can be transformed from
lower normal forms to higher normal forms
• That normalization and ER modeling are used
concurrently to produce a good database design
• That some situations require denormalization to
generate information efficiently
16
Database Systems, 10th
Edition
Chapter 6 Key Points
• Normalization minimizes data redundancies
• First three normal forms (1NF, 2NF, and 3NF)
are most commonly encountered
• Table is in 1NF when:
– All key attributes are defined
– All remaining attributes are dependent on
primary key
17
Database Systems, 10th
Edition
Chapter 6 Key Points(cont’d)
• Table is in 2NF when it is in 1NF and contains no partial
dependencies
• Table is in 3NF when it is in 2NF and contains no
transitive dependencies
• Table that is not in 3NF may be split into new tables until
all of the tables meet 3NF requirements
• Normalization is important part—but only part—of the
design process
• Tables are sometimes denormalized to yield less I/O,
which increases processing speed
18
Database Systems, 10th
Edition
Purchase answer to see full
attachment