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INF2603 EXAM PACK 2023
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INF2603EXAM PACK
2023
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Contents
Chapter 1: Database Systems ........................................................................................................................... 4
Types of databases ......................................................................................................................................... 4
Historical Roots: Files and File Systems ...................................................................................................... 4
Basic file terminology: ............................................................................................................................... 4
Structural and Data dependence: ............................................................................................................ 5
Data Redundancy ....................................................................................................................................... 5
Database Systems .......................................................................................................................................... 5
The database system environment ......................................................................................................... 5
DBMS Functions ......................................................................................................................................... 6
Managing the DB System .......................................................................................................................... 6
Chapter 2: Data Models ..................................................................................................................................... 7
The Importance of Data Models .................................................................................................................. 7
Data Model Basic Building Blocks ................................................................................................................ 7
Business Rules ................................................................................................................................................. 7
Discovering Business Rules ....................................................................................................................... 7
The Evolution of Data Models ...................................................................................................................... 7
The Hierarchical Model ............................................................................................................................. 7
The Network Model ................................................................................................................................... 7
The Relational Model ................................................................................................................................ 7
The Entity Relationship Model ................................................................................................................. 8
The Object-Orientated (OO) model ......................................................................................................... 8
Degrees of data abstraction ......................................................................................................................... 9
Chapter 3: The Relational Database Model .................................................................................................. 10
A logical view of data ................................................................................................................................... 10
Tables and their characteristics ............................................................................................................. 10
Attributes and Domains .......................................................................................................................... 10
Degree of cardinality ............................................................................................................................... 11
Keys ................................................................................................................................................................ 11
Integrity Rules ............................................................................................................................................... 12
The data dictionary and the system catalogue ........................................................................................ 12
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Relationships within the relational database ........................................................................................... 13
The 1:* Relationship ................................................................................................................................ 13
The 1:1 Relationship ................................................................................................................................ 13
The *:* Relationship ................................................................................................................................ 13
Data redundancy revisited .......................................................................................................................... 14
Indexes ........................................................................................................................................................... 14
Codd’s relational database rules ................................................................................................................ 14
Chapter 5: Entity relationship (ER) modelling .............................................................................................. 16
The entity relationship (ER) model ............................................................................................................ 16
Entities ....................................................................................................................................................... 16
Attributes .................................................................................................................................................. 16
Relationships............................................................................................................................................. 18
Multiplicity ................................................................................................................................................ 18
Existence dependence ............................................................................................................................. 18
Relationship strength .............................................................................................................................. 18
Weak entities ............................................................................................................................................ 19
Relationship participation ....................................................................................................................... 19
Relationship degree ................................................................................................................................. 19
Recursive relationships ........................................................................................................................... 20
Composite entities ................................................................................................................................... 20
Developing an ER diagram .......................................................................................................................... 21
Database design challenges: Conflicting goals ......................................................................................... 21
Chapter 6: Advanced Data Modelling ............................................................................................................ 22
The extended entity relationship model (EERM) .................................................................................... 22
Entity supertypes and subtypes ............................................................................................................. 22
Specialisation hierarchy .......................................................................................................................... 22
Inheritance ................................................................................................................................................ 22
Subtype Discriminator ............................................................................................................................. 22
Disjoint and overlapping constraints .................................................................................................... 22
Completeness constraint ........................................................................................................................ 23
Specialisation and generalisation .......................................................................................................... 23
Composition and Aggregation................................................................................................................ 23
Entity Clustering ........................................................................................................................................... 24
Entity integrity: Selecting primary keys .................................................................................................... 24
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Natural keys and primary keys ............................................................................................................... 24
Primary key guidelines ............................................................................................................................ 24
When to use composite primary keys .................................................................................................. 25
When to use surrogate primary keys .................................................................................................... 25
Design cases: Learning flexible database design ..................................................................................... 25
Design case #1: Implementing 1:1 relationships ................................................................................. 25
Design case #2: Maintaining history of time-variant data ................................................................. 26
Design case #3: Fan traps........................................................................................................................ 26
Design case #4: Redundant relationships ............................................................................................. 27
Data modelling checklist ............................................................................................................................. 27
Chapter 7: Normalization of database tables ............................................................................................... 28
Database tables and normalisation ........................................................................................................... 28
The need for normalization ........................................................................................................................ 28
The normalization process .......................................................................................................................... 28
Conversion to first normal form ............................................................................................................ 28
Conversion to second normal form ....................................................................................................... 29
Conversion to third normal form ........................................................................................................... 30
Improving the design ................................................................................................................................... 30
Evaluate PK assignments ......................................................................................................................... 30
Evaluate naming conventions ................................................................................................................ 30
Refine attribute atomicity....................................................................................................................... 30
Identify new attributes ............................................................................................................................ 30
Identify new relationships ...................................................................................................................... 30
Refine primary keys as required for data granularity ......................................................................... 30
Maintain historical accuracy ................................................................................................................... 31
Evaluate using derived attributes .......................................................................................................... 31
Surrogate key considerations ..................................................................................................................... 31
Higher level normal forms .......................................................................................................................... 31
The Boyce-Codd normal form (BCNF) ................................................................................................... 31
Forth normal form (4NF) ......................................................................................................................... 31
Normalization and database design .......................................................................................................... 31
De-normalization .......................................................................................................................................... 32
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