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
Section ID Number
Instructor ID Number
Days of the Week
Time
Start Date
End Date
Student ID Number
Last Name
First Name
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
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