ICDL

Software Applications

- Database Concepts

Unit

6 Data and Data Representation

• Database Concepts– File Structure– Relationships

• Database Design– Data Types– Design Considerations

File and Database Concepts

• A database is a collection of information

• Databases are typically stored as computer files

• A structured file is similar to a card file or Rolodex because it uses a uniform format to store data for each person or thing in the file

File and Database Concepts

• A field contains the smallest unit of meaningful information

• Each field has a unique field name that describes its contents

• A field can be either variable length or fixed length.

Section A

File and Database Concepts

• A record refers to a collection of data fields

• Each kind of record is referred to as a record type

• A record type is similar to a blank form, – it is usually shown without any data in

the fields

Section A

File and Database Concepts

File and Database Concepts

Student Information

CNA-Q ID NumberLast NameFirst Name

EmailAddress

CityProgram

Sponsor ID Number

Sponsor Information

Sponsor ID NumberCompany Name

Contact Last NameContact First Name

EmailTelephone

Fax NumberAddress

City

Course Information

Course ID NumberPeopleSoft ID Number

Course NameInstructor ID Number

Instructors

Instructor ID NumberLast NameFirst Name

FacultyEmail

Office Telephone

Financial Accounts

CNA-Q Student ID NumberTerm Number

Cost Per CourseNumber of Courses

Amount for TermAmount Paid

Amount Owing

Faculty Advisors

CNA-Q Student ID NumberInstructor ID Number

Possible Tables in a CNA-Q Database:

Data and Data Representation

• Database Concepts– File Structure– Relationship and Cardinality

• Database Design– Data Types– Design Considerations

Section AFile and Database Concepts

• A data file that contains only one record type is often referred to as a flat file

• In contrast, a database can contain a variety of different record types

• In database jargon, a relationship is an association between data stored in different record types

• Cardinality refers to the number of associations that can exist between two record types

Section AFile and Database Concepts

• A one-to-one relationship means that a record in one record type is related to only one record in another record type

• Example:– A single grade report is related to only one

student.

Section AFile and Database Concepts

File and Database Concepts

• When one record is related to many records in another table, the relationship is referred to as a one-to-many relationship

• Example:– Instructor records to student advisees

File and Database Concepts

• A many-to-many relationship means that one record in a particular record type can be related to many records in another record type, and vice versa

• Example:– Student records to course enrollment

File and Database Concepts

• A relational database stores data in a collection of related tables

• Each table (also called a “relation”) is a sequence, or list, of records.

• All of the records in a table are of the same record type

Section A

File and Database Concepts

Student Information

CNA-Q ID NumberLast NameFirst Name

EmailAddress

CityProgram

Sponsor ID Number

In a Relational Database, records in two or more tables may be related by common fields:

Sponsor Information

Sponsor ID NumberCompany Name

Contact Last NameContact First Name

EmailTelephone

Fax NumberAddress

CityOne-to-Many RelationshipMany

records can have the

same Sponsor ID

Number

Only one record can have each Sponsor ID

Number

Data and Data Representation

• Database Concepts– File Structure– Relationship and Cardinality

• Database Design– Data Types– Design Considerations

Database Design

• The data that can be entered into a field depends on the field’s data type

• From a technical perspective, a data type specifies the way data is represented on the disk and in RAM

• From a user perspective, the data type determines the way that data can be manipulated

Database Design

• The two most common data types are numeric and character

• A database designer can assign a numeric data type to fields containing numbers that will be manipulated mathematically by adding, averaging, multiplying, and so forth

Database Design

• For fields that contain data that would not be used for calculations, a database designer can specify a character (or string) data type.– In Access, this is referred to as “Text”

type.

• Text fields sometimes hold data that looks like numbers, but doesn’t need to be mathematically manipulated

• Some file and database management systems provide additional data types such as date and logical

• The date data type is used to store dates in a format that allows them to be manipulated

• The logical data type is used to store true/false or yes/no data using minimal storage space

Database Design

Database Design

• A computed field is a calculation that a DBMS performs during processing, and then temporarily stores in a memory location.

• An efficiently designed database uses computed fields whenever possible because they do not require disk storage space

Database Design

Pass Grade:

80

Student’s Average

Pass/Fail Term?

???? ????

Module 1 Module 2 Module 3 Module 4 Module 5 Module 6 Module 7

80 100 76 94 42 100 90

Pass/Fail? Pass/Fail? Pass/Fail? Pass/Fail? Pass/Fail? Pass/Fail? Pass/Fail?

Computed Fields

Data and Data Representation

• Database Concepts– File Structure– Relationship and Cardinality

• Database Design– Data Types– Design Considerations

Database planning considerations

• Database purpose

• Number of tables and type of information

• Fields in each table

• Information to extract

• How to enter data

• Reports

Database Purpose

• To store and organize information for the CNA-Q ICDL Training and Testing Centre.

Number of Tables and Type of Information

• Instructors

• Class Sections

• Candidates/Students

• Module Tests

Instructor ID Number

Last Name

First Name

Email

Section ID Number

Instructor ID Number

Days of the Week

Time

Start Date

End Date

Student ID Number

Last Name

First Name

Email

Section ID Number

Student ID Number

Pass Module 1

Pass Module 2

Pass Module 3

Pass Module 4

Pass Module 5

Pass Module 6

Pass Module 7

Database planning considerations

• Database purpose

• Number of tables and type of information

• Fields in each table

• Information to extract

• How to enter data

• Reports

Extracting information is called Querying a database:

Single Table Queries

Multi-Table Queries

Conditional QueriesData can be entered into tables directly, or by using Forms:

Simple Form Creation

Custom Form Creation

We can generate reports for a number of purposes:

Class Lists

Candidate Report Cards