1. Introduction to Database
BUS 782

2. File Concepts
File consists of a group of records. Each record contains a group of fields.
Example: Student file
SID Sname Major Sex GPA
S1 Peter CIS M 3.0
S3 Paul ACCT M 2.7
S5 Mary CIS F 3.2

3. Examples Database file Spreadsheet file XML file
Created and managed by a DBMS
Spreadsheet file
Created and managed by a spreadsheet software
XML file
Comma-Delimited file – A text file that can be processed by any programming languages, DBMS and spreadsheet.
"s5","peter",3.5
"s1","paul",3
"s7","mary",2
Comma-Delimited file demo: stdata.txt
Access –External Data/Text File
Excel – Data/Get External Data/From Text

4. XML <?xml version="1.0" ?> <Books> <Book>
<ISBN> </ISBN>
<Authors>
<AuthorName>John Smith</AuthorName>
<AuthorName>Peter Chen</AuthorName>
<AuthorName>David Chao</AuthorName>
</Authors>
<Price> $45.00</Price>
<Description>This is a grerat book</Description>
</Book>
<ISBN> </ISBN>
<AuthorName>Adam Smith</AuthorName>
<Price> $25.00</Price>
<Description>This is a second great book</Description>
</Books>

5. Word 2007 DOCX

6. Relational Database Data is logically structured within relations.
Each relation is a table (file) with named columns (attributes, fields) and rows (records).

7. File Concepts
Each file must have one key field. Key field uniquely determines a record in a file.
Grouping field: A filed that can be used to group records, for example, Major in the Student file.
Calculated filed: A field whose value is derived from existing fields, for example, Age can be calculated from DateOfBirth.
Each field can hold only one value.

8. Basic File Processing Sorting/Grouping Compute subtotals
Selecting records meeting criteria

9. Example Student file What information can be retrieved from this file?
SID Sname Major Sex GPA
S1 Peter CIS M 3.0
S3 Paul ACCT M 2.7
S5 Mary CIS F 3.2
What information can be retrieved from this file?

10. File Organization and Access
Sequential file (heap file): Records are organized in sequence in the order in which they are entered.
File access:
Sequential access
Direct access
Index file: Key + record’s location (address)

11. Direct access time
1. Seek time: This is the time needed to mechanically position the read/write head on the correct track.
2. Rotational delay: This is the time needed to wait for the beginning of the required block to rotate into position under the read/write head
3. Data transfer time: Time needed to transfer the data.

12. Other file organization
Hash file (direct file)
Hashing function, H
Record location = H(key)
Search a record with key K1:
Location of record with key K1 = H(K1)

13. Database Concepts A database is a collection of related files.
Support business operations
Provide information
A database management system is a software that enables users to create and maintain a database.

14. Major Functions of Database Management
Creating a database
Analysis: Entity-Relationship Diagram
Design: Design file structure
Implementation
Accessing a database
Updating a database

15. Database design objectives
Eliminate data duplication.
Inconsistent data, double entry, waste space
Link related records in related tables.
Example:
StudentTable: SID, Sname, Address, Major,
StudentAccountTable: SID, Sname, Address, Balance
Company Database
Department table: DID, Dname, DepOffice, DepPhone
Employee table: EID, Ename, Address, , Salary
Note: A table’s key field plays an important role in linking related records.

16. An example of database design problem
Design a database for a company to keep track of employees, departments and projects. The company is organized into departments. Each department has a unique number, name. Each department controls a number of projects, each of which has a unique number, and name. Several employees may work on the same project. We store each employee's SSN, name, address, salary, and birthday. An employee is assigned to one department but may work on several projects.

17. Entity-Relationship Diagram
An entity is a “thing” in the real world, such as a person, place, event for which we intend to collect data.
An entity has certain characteristics (properties) known as attributes (fields).
Entity type(Entity set): a set of similar entities.
A business environment may involve many entity types.
University: Faculty, Student, Course
Department, Employee, Dependent
Sales person, Customer, Order

18. Entity-Relationship Diagram
Relationship: Interaction between entity types.
Faculty teach Course, Faculty advise Student
Customer open Account, Customer purchase Product.
Binary relationship: A relationship involves two entity types.
Three types of binary relationship:
1:1, 1:M, M:M