1. Week 11: Database Management System
READING: Chapter 12.3

2. Database Management System
EECS Computer Use: Fundamentals
Database Management System
Database: A structured set of data
Database Management System (DBMS): A combination of software and data, including:
Physical database: A collection of files that contain the data
Database engine: software that supports access to and modification of the database contents
Database schema: a specification of the logical structure of the data stored in the database 2

3. Database Management System
EECS Computer Use: Fundamentals
Database Management System
Specialized database languages allow the user to:
specify the structure of data
add, modify, and delete data;
query the database to retrieve specific stored data 3

4. Database Management System
EECS Computer Use: Fundamentals
Database Management System 4

5. Database Management System
EECS Computer Use: Fundamentals
Database Management System
A schema is a description of the entire database structure used by the database software to maintain the database
A subschema is a description of only that part of the database that is particular to a user’s needs 5

6. Database Management System
EECS Computer Use: Fundamentals
Database Management System
A layered approach hides the complexities of database implementation:
User sees data in terms of the applications
The application sees data in terms of the database model
The “DBMS” sees data as it is organized 6

7. Database Management System
EECS Computer Use: Fundamentals
Database Management System
Advantages of the layered approach include :
Simplification of the design process
Better control of access
Data independence
Applications can be written in terms of simple, conceptual views of the data – the database model 7

8. EECS 1520 -- Computer Use: Fundamentals
Database Models
A database model is a conceptual view of how to organize and manipulate data
The most popular one is the Relational Model 8

9. EECS 1520 -- Computer Use: Fundamentals
Relational Model
In a “Relational DBMS”, the data items, and the relationships among them, are organized into rectangular tables:
As with spreadsheets, these tables consist of rows and columns.
Each table is called a relation
The rows are called tuples or records
The columns are called attributes 9

10. EECS 1520 -- Computer Use: Fundamentals
Database 10

11. EECS 1520 -- Computer Use: Fundamentals
Database Table
We can express the schema for this database table as follows:
Movie (MovieId: key, Title, Genre, Rating) 11

12. EECS 1520 -- Computer Use: Fundamentals
Database Table
A partial CUSTOMER table: 12

13. Database Table We can express the schema for this database table as:
EECS Computer Use: Fundamentals
Database Table
We can express the schema for this database table as:
Customer (CustomerId: key, Name, Address, CreditCardNumber) 13

14. EECS 1520 -- Computer Use: Fundamentals
Relationships
A table can represent a collection of relationships between objects. The “RENTS” table relates Customers to the Movies they have rented by their respective Ids. 14

15. Database Table We can express the schema for a relationship:
EECS Computer Use: Fundamentals
Database Table
We can express the schema for a relationship:
Note: the absence of a key field
Rents (CustomerId, MovieId, DateRented, DateDue) 15

16. Relational Operations
EECS Computer Use: Fundamentals
Relational Operations
There are 3 fundamental operations that can be used to manipulate the tables in a database:
SELECT
Extracts rows (tuples) from a table (relation)
PROJECT
Extracts columns (attributes) from a table (relation)
JOIN
Combines 2 tables (relations) into 1 16

17. Relational Operations
EECS Computer Use: Fundamentals
Relational Operations
We can express these operations with a simple syntax.
This operation creates a new relation (named NEW) by extracting all rows from the MOVIE table that have a RATING of PG.
NEW ← SELECT from MOVIE where RATING = “PG” 17

18. Relational Operations
EECS Computer Use: Fundamentals
Relational Operations 18

19. EECS 1520 -- Computer Use: Fundamentals
SELECT
MovieId
Title
Genre
Rating
102
Back to the Future
comedy adventure PG
104
Field of Dreams
fantasy drama
The NEW relation. 19

20. Relational Operations
EECS Computer Use: Fundamentals
Relational Operations
The same syntax can be used for the other operations.
This operation creates a new relation (named PGmovies) that extracts 2 attributes from the NEW relation.
PGmovies ← PROJECT MovieId, Title from NEW 20

21. EECS 1520 -- Computer Use: Fundamentals
PROJECT
MovieId
Title
102
Back to the Future
104
Field of Dreams
The PGmovies relation. 21

22. Relational Operations
EECS Computer Use: Fundamentals
Relational Operations
A JOIN creates a new relation by combining 2 relations according to some criterion.
TEMP1 ← JOIN CUSTOMER and RENTS
where CUSTOMER.CustomerId = RENTS.CustomerId
CUSTOMER
RENTS 22

23. EECS 1520 -- Computer Use: Fundamentals
JOIN
CustomerId
Name
Address
CreditCardNumber
MovieId
DateRented
DateDue
101
Dennis Cook
789 Main
102
08/11/2010
15/11/2010
104
04/11/2010
14/11/2010
Doug Nickle
456 Second
09/11/2010
11/11/2010
103
Randy Wolf
12 Elm
07/11/2010
10/11/2010
05/11/2010
Amy Stevens
Yellow Brick Road
107
105
Susan Klaton
654 Lois Lane
1033
13/11/2010
Chris Stein
1010 Abbey Road
7442
06/11/2010
TEMP1 23

24. Relational Operations
EECS Computer Use: Fundamentals
Relational Operations
The PROJECT operation can be used to remove the attributes we don’t want…
RENTALS ← PROJECT Name, Address, MovieId from TEMP1 24

25. Relational Operations
EECS Computer Use: Fundamentals
Relational Operations
The RENTALS relation.
Name
Address
MovieId
Dennis Cook
789 Main
102
104
Doug Nickle
456 Second
101
Randy Wolf
12 Elm
Amy Stevens
Yellow Brick Road
107
Susan Klaton
654 Lois Lane
1033
Chris Stein
1010 Abbey Road
7442 25

26. Relational Operations
EECS Computer Use: Fundamentals
Relational Operations
Now, JOINing RENTALS to PGmovies…
…creates a table of customers who have rented PG movies.
PGrenters ← JOIN RENTALS and PGmovies
where RENTALS.MovieId = PGmovies.MovieId
Name
Address
MovieId
Title
Dennis Cook
789 Main
102
Back to the Future
104
Field of Dreams
Randy Wolf
12 Elm 26

27. Structured Query Language
EECS Computer Use: Fundamentals
Structured Query Language
Structured Query Language (SQL)
A comprehensive database language for managing relational databases. 27

28. EECS 1520 -- Computer Use: Fundamentals
Queries in SQL
select attribute-list from table-list where condition
select Title from MOVIE where Rating = 'PG‘
select Name, Address from CUSTOMER
select * from MOVIE where Genre like '%action%‘
select * from MOVIE where Rating = 'R' order by Title 28

29. Modifying Database Content
EECS Computer Use: Fundamentals
Modifying Database Content
Insert into CUSTOMER values (9876, ‘John Smith’, ‘602 Greenbriar Court’, ‘ ’)
Update MOVIE set Genre = ‘thriller drama’ where title = ‘Unbreakable’
Delete from MOVIE where Rating = ‘R’ 29

30. EECS 1520 -- Computer Use: Fundamentals
Database Design
Entity-relationship (ER) modeling
A popular technique for designing relational databases.
ER Diagram
Chief tool used for ER modeling.
Captures the important record types, attributes, and relationships in a graphical form. 30

31. EECS 1520 -- Computer Use: Fundamentals
Database Design
These designations show the cardinality constraint of the relationship: 31