1. Information Systems Database Management
Chapter 12.3+
Information Systems
Database Management

2. Database Management Systems
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.

3. Database Management Systems
Specialized database languages allow the user to:
specify the structure of data;
add, modify, and delete data;
query the database to retrieve specific data.

4. Database Management Systems

5. Databases
Databases are a recent development in the management of large amounts of data.
As paper file systems were “computerized” each application was implemented separately with its own data set.
These systems were riddled with both corrupt data and redundant data, none of which could be shared.

6. Parking doesn’t need to see your grades.
Databases
The integration of separate systems into one database resolved these issues, but introduced new ones.
With all data shared, control of access to the data becomes a major concern.
Parking doesn’t need to see your grades.

7. Database Management Systems
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.

8. Database Management Systems
A layered approach hides the complexities of database implementation.
User sees data in terms of the application.
The application “sees” data in terms of the database model.
The DBMS “sees” data as it is organized.

9. Database Management Systems
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.

10. Database Models
A database model is a conceptual view of how to organize and manipulate data.
The most popular one is the Relational Model.

11. The 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.
The columns are called attributes.

12. The Relational Model
Of course, different authors adopt different terms. There is a commonly used, alternate set of names:
Relations are also called tables.
A tuple can be referred to as a record,
and in this terminology
a record is a collection of related fields.

13. An Example

14. A Sample Movie Table

15. Movie (ID:key, Title, Genre, Rating)
A Database Table
We can express the schema for this table as follows:
Movie (ID:key, Title, Genre, Rating)
Unique values

16. A Partial Customer Table

17. A Partial Customer Table
We can express the schema for this table as:
Customer (ID:key, Name, Address, CreditCardNumber)

18. Relationships A table can represent relationships between objects.
The Rents table relates Customers to the Movies they’ve rented, by their respective IDs.

19. Rents (CustomerId, MovieId, DateRented, DateDue)
Relationships
We can also express the schema for a relationship:
Rents (CustomerId, MovieId, DateRented, DateDue)
Note the absence of a key field.

20. Relational Operations

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

22. Relational Operations
The result of any relational operation is a new relation.
We can express these operations with a simple syntax.
PGmovies ← SELECT from Movie where Rating = “PG”
This operation creates a new relation (PGmovies) by copying all the rows from the Movie table that have a Rating of PG.

23. Relational Operations: SELECT
The PGmovies relation.

24. Relational Operations
The same syntax can be used for the other operations.
PGtrimmed ← PROJECT MovieId, Title from PGmovies
This operation creates a new relation that copies two attributes from the PGmovies relation.

25. Relational Operations: PROJECT
The PGtrimmed relation.

26. Relational Operations
A JOIN creates a new relation by combining 2 relations according to some criterion.
Rentals ← JOIN Customer and Rents where Customer. Id = Rents.CustomerId

27. Relational Operations: JOIN
The Rentals relation.

28. Relational Operations: PROJECT
The PROJECT operation can be used to remove the attributes we don’t want…
RentalsTrimmed ← PROJECT Name, Address, MovieId from Rentals

29. Relational Operations
The RentalsTrimmed relation.

30. Relational Operations
Now, JOINing RentalsTrimmed to PGtrimmed …
PGrenters ← JOIN RentalsTrimmed and PGtrimmed where RentalsTrimmed.MovieId = PGtrimmed .MovieId
…creates a table of customers who have rented PG movies.

31. Structured Query Language

32. Structured Query Language
Structured Query Language (SQL)
sometimes pronounced “SeQueL”
a comprehensive language for managing relational databases.
Implements the basic dBase operations, but with a different set of key words.

33. Structured Query Language
SQL includes commands to:
create new databases
create new tables
insert/delete records
update records
create views
set permissions on tables, procedures, and views
execute queries

34. Queries in SQL - PROJECT
All SQL queries are created with SELECT.
SELECT attribute-list FROM table WHERE attribute meets condition
Conditional Operators: =, <>, >, <, >=, <=, BETWEEN, LIKE, IN

35. Queries in SQL - SELECT
SELECT * FROM table WHERE attribute meets condition
* is a wild card symbol. It represents “all attributes” which means “the whole record”.

36. Queries in SQL - JOIN
SELECT * FROM table1 INNER JOIN table2 ON condition
The JOIN is performed first, then the SELECT. Types of JOINs: INNER, LEFT, RIGHT, FULL

37. Queries in SQL - Examples
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

38. 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'

39. Database Design

40. Database Design Entity-relationship (ER) modeling ER Diagram
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.

41. Database Design
These designations show the cardinality constraint of the relationship