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ITIS 1P97 Study Guide - Final Guide: Database, Expected Value Of Perfect Information, Pessimism

Information Technology Information Systems
Course Code
Bob Sproule
Study Guide

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Database Management and Development:
Database structure
Entity Relationship Modeling
Field types (Primary Keys, Foreign Keys, etc.)
Linking Tables
Working with queries
Interpretation of queries given a database.
A database is a share, integrated repository. It houses end-user’s data and metadata
A Database Management System (DBMS) is a collection of programs that manages
database structure and controls access to the data
Data Relationships:
One- to- many relationships: E.g a painter may paint many paintings, but each painting is
only painted by one painter.
Many-to-many relationships- A student may take many courses and each course can be
taken by many students
One-to –one relationships : A salesperson is assigned to a company car
Hierarchical Model: Relationships between data must fit an upside-down tree or parent-
child structure
-Data can only have one-to-many relationships
-Data must always be retrieved from the top down
-Not flexible
Network Model
- Allows child to have more than one parent
- More flexible than the hierarchical model but difficult to design and use properly
- Very complex for programming
Rational Model
Developed by E.F. Cobb in 1970 (IBM)
Conceptually simple
Easy for end users to construct queries and retrieve data on an ad-hoc
- Each column in the table is a field or attribute
- Each tow in the table is a record
Primary Keys: Each table must include one field ( or set of fields) that uniquely
identifies each record
e.g: The student ID field
The DBMS will ensure there is no duplication allowed in the primary key field
A composite key is when the combination of two fields is a unique identifier
Foreign Keys: We link tables by putting the primary key of one table as a field in another
In the second table, this field is called a foreign key.

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Entity Integrity
All records must be uniquely identified (no nulls or duplicates)
Referential Integrity
Foreign key references must match a primary key in the referenced table
Entities – a person, place, ev ent or thing about which we intend to collect data
Relationships – one-to-one, one-to-many, many-to-many
Attributes – The characteristics of the entity that we want to record
Primary key
A process for assigning attributes to entities
Produces good table structures
Reduces data redundancies to prevent:
Update anomalies
Addition anomalies
Deletion anomalies
Attribute B is dependent on attribute A if whenever the value of A is x, the value
of B is y
Attribute A determines attribute B if all of the rows in the table which agree for A
must also agree for B
Student Number -> Student Name
Employee SIN -> Employee Name
Normal Form
First Normal Form
No repeating groups and all values need to be “atomic”
All attributes are dependent on the primary key, or at least part of a
composite key
Second Normal Form
No non-key attribute is partially dependent on just a part of a composite
primary key

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Only happens with a composite key - If there is a single attribute primary
key, a table in 1NF is also in 2NF
Third Normal Form
Remove transitive dependencies
A transitive dependency exists if an attribute, which is not part of
the primary key, determines another non-key attribute
Data Dictionary: Contains details about the data
Include: Format, Sizes, Relationships, and Security
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