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

Student Information CNA-Q ID Number Last Name First Name Address City Program Sponsor ID Number Sponsor Information Sponsor ID Number Company Name Contact Last Name Contact First Name Telephone Fax Number Address City Course Information Course ID Number PeopleSoft ID Number Course Name Instructor ID Number Instructors Instructor ID Number Last Name First Name Faculty Office Telephone Financial Accounts CNA-Q Student ID Number Term Number Cost Per Course Number of Courses Amount for Term Amount Paid Amount Owing Faculty Advisors CNA-Q Student ID Number Instructor 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 A File 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 A File 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 A 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 Number Last Name First Name Address City Program Sponsor ID Number In a Relational Database, records in two or more tables may be related by common fields: Sponsor Information Sponsor ID Number Company Name Contact Last Name Contact First Name Telephone Fax Number Address City One-to-Many Relationship Many 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

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 1Module 2Module 3Module 4Module 5Module 6Module 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 Queries  Data 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