1. By Anil Kumar

2. Objectives Review database theory and history
Review relational database concepts
Learn about the evolution of data access technologies
By Anil Kumar

3. Agenda
Databases
Relational Databases
By Anil Kumar

4. Databases Databases
Virtually all interesting applications require a structured, persistent data store
E-Commerce: placing an order, fulfilling an order
HR: Personnel data
Sales
CRM: Customer data
Games
Database needs vary with the type of application
Transaction Processing/OLTP
Business Intelligence/Data Warehouse/OLAP
By Anil Kumar

5. Databases Database Requirements
Can store, view and modify data
Can move, copy and transform data
Can backup and restore data
Enforces data integrity rules
Is scaleable and available
High number of users
Lots of data
High throughput with low response time
Is secure
Facilitates application development
By Anil Kumar

6. Databases Evolution of Database Technology
File-based
Hierarchical
Network
Relational (RDBMS)
Object-oriented
XML
By Anil Kumar

7. Agenda
Databases Theory and History
Relational Databases
By Anil Kumar

8. Relational Databases Tables
Table (relation, entity)
A collection of data about a specific type of thing
Organized in rows and columns
Column (attribute, field)
Describes part of an entity (e.g. FirstName)
Has a data type (e.g. integer, character, binary)
Can be null
Row (tuple, record)
A single instance of data in a table
Each row is unique
AuthID
FirstName
LastName 1
Joe
Smith 2
Diane
Jones
By Anil Kumar

9. Relational Databases Relating Data
Tables can be related through primary/foreign key relationships (e.g., a book has an author)
Primary key
Guarantees the uniqueness of a row
Can be composed of one or more columns
Ensures entity integrity
Foreign key
Establishes logical relationship between tables
One or more columns of a table that match the primary or alternate key of another table
Referential integrity
Relational databases do NOT get there name because they can relate data. They get their name from set theory: a relation is the set-theoretic term for a table.
Primary/foreign key relationships are THE way data is related in a relational database.
By Anil Kumar

10. Relational Databases Relating Data
Schema diagram depicts tables, columns, primary keys, foreign keys
Books
BookID
AuthID
Title
Type
Authors
AuthID
FirstName
LastName 1 ∞
Schema Diagram
By Anil Kumar
By Anil Kumar

11. Relational Databases Relating Data
Books Table
Primary Key
BookID
AuthID
Title
Type 1 2
My Life as a DBA
Autobiography
Database Handbook
Reference
PK/FK Relationship
Foreign Key
AuthID
FirstName
LastName 1
Joe
Smith 2
Diane
Jones
Authors Table
By Anil Kumar

12. Relational Databases Types of Relationships
One-to-One (1:1)
One row in table X matches one row in table Y
A book has at most one Library of Congress entry
One-to-Many (1:M)
One row in table X matches 0+ rows in table Y
A publisher publishes one or more books
Many-to-Many (M:N)
1+ rows in table X matches 1+ rows in table Y
An author writes one or more books; a book is written by one or more authors 1 1
Books
LoC Entries
Publishers 1 M
Books M
Authors N
Books
By Anil Kumar

13. Relational Databases M:N Relationships
More complex
Can result in very large tables (repeated data)
Difficult to ensure data integrity
The remedy: Create a third table
The third table contains the primary key of the two original tables in a composite key
Data is repeated in the third table, but not in the two original tables
Authors 1 M
BookAuth M 1
Books
By Anil Kumar

14. Relational Databases M:N Relationships1 ∞
Data is duplicated here 1 1 ∞ ∞
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15. Relational Databases Normalization/Denormalization
The process of breaking large tables into multiple smaller tables
Goal: minimize redundant data, maximize correctness
Improves performance for updates
Desirable in transaction-based applications
Denormalization
The process of combining smaller tables into fewer larger tables
Goal: improve performance
Introduces redundant data
Improves performance for reads
Desirable in data warehouse applications
By Anil Kumar

16. Relational Databases Joins
A join is a way of combining data in multiple tables, usually by resolving primary key/foreign key relationships
Product table
Vendor table
Product
Cost
Vendor
Vendor
State
Contact
Widget
$10
Acme
Acme MA
Linda A.
Thingy $5
Acme
Blecco WA
Adam P.
Widget $8
Blecco
Foobar
$25
Blecco
By Anil Kumar

17. Relational Databases Joins
Result of a natural join
Product
Cost
Vendor
State
Contact
Widget
$10
Acme MA
Linda A.
Thingy $5
Acme MA
Linda A.
Widget $8
Blecco WA
Adam P.
Foobar
$25
Blecco WA
Adam P.
By Anil Kumar

18. Relational Databases Structured Query Language (SQL)
Standard language for accessing a relational database, standardized by American National Standards Institute (ANSI); SQL-92
Open, but not really
Common functions are mostly the same across products
Most vendors have proprietary extensions
Subsets of SQL
Data Definition Language (DDL)
Data Manipulation Language (DML)
Data Control Language (DCL)
By Anil Kumar

19. Relational Databases DDL Examples
Used to create and modify database objects
CREATE DATABASE Bookstore
CREATE TABLE tBooks (
BookID INT IDENTITY(1,1) PRIMARY KEY,
Title VARCHAR(30) NOT NULL,
PubDate DATE NOT NULL,
[Description] VARCHAR(50),
Category INT NOT NULL )
By Anil Kumar

20. Relational Databases DML Examples
Select data to view
SELECT * FROM tAuthors
SELECT AuthID, FirstName, LastName
FROM tAuthors
SELECT AuthID, FirstName, LastName, Phone
FROM tAuthors
WHERE City = ‘Boston’
SELECT FirstName, LastName, Phone
FROM tAuthors
WHERE AuthID = 249
By Anil Kumar

21. Relational Databases DML Examples
Using SELECT to join tables
SELECT AuthID, FirstName, LastName, Phone,
BookID, Title, PubDate, Description
FROM tAuthors, tBooks
WHERE tAuthors.AuthID = tBooks.AuthID
SELECT AuthID, FirstName, LastName, Phone,
BookID, Title, PubDate, Description
FROM tAuthors INNER JOIN tBooks
ON tAuthors.AuthID = tBooks.AuthID
By Anil Kumar

22. Relational Databases DML Examples
Insert, update and delete data
INSERT INTO tBooks
(Title, PubDate, [Description], Category)
VALUES
(‘Database Design’, GETDATE(),
‘How to design a database’, 3)
UPDATE tAuthors
SET Phone = ‘ ’
WHERE AuthID = 5
DELETE FROM tAuthors
WHERE AuthID = 5
By Anil Kumar

23. Relational Databases DCL Examples
Set security options on database objects
GRANT INSERT, UPDATE, DELETE
ON tAuthors
TO Mary, John
REVOKE CREATE TABLE FROM Joe
DENY ALL
ON tAuthors, tBooks
TO Sally
By Anil Kumar

24. Relational Databases Views
A view is a virtual table
Abstracts the underlying table structures
Abstracts a (possibly complex) query
Provides security abstraction from table
In SQL Server 2000, a view can be
Indexed
Updated and inserted into
By Anil Kumar

25. Relational Databases View Definition Example
CREATE VIEW vwCustomerOrders AS
SELECT o.OrderId, c.CompanyName
FROM Customers c
INNER JOIN Orders o
ON c.CustomerID = O.CustomerID
ORDER BY o.OrderId
By Anil Kumar

26. Relational Databases View Usage Example
SELECT *
FROM vwCustomerOrders
WHERE CompanyName = 'My Favorite Customer'
OrderId
CompanyName
101
My Favorite Customer
137 …
By Anil Kumar

27. Relational Databases Stored Procedures
A group of SQL statements that runs within the database
Not part of SQL standard
Provides greater performance
Can control access to data
Can accept parameters
Can return data
Output parameters
Return values
Result set
By Anil Kumar

28. Relational Databases Stored Procedure Example
CREATE PROCEDURE nchar(5) AS
SELECT ProductName, Total=SUM(Quantity)
FROM Products P, [Order Details] OD, Orders O, Customers C
WHERE C.CustomerID
AND C.CustomerID = O.CustomerID
AND O.OrderID = OD.OrderID
AND OD.ProductID = P.ProductID
GROUP BY ProductName
By Anil Kumar

29. Relational Databases Stored Procedure Examples
exec CustOrderHist 'alfki'
ProductName
Total
Aniseed Syrup 6
Chartreuse verte 21
...
By Anil Kumar

30. Relational Databases Stored Procedure Examples
Use RETURN statement to return status
0 is default in SQL Server
Can only be numeric
Use OUTPUT parameters to return results
RETURN 1
CREATE PROCEDURE INT OUTPUT
...
= ColumnName FROM Table
By Anil Kumar

31. Relational Databases Triggers
Like stored procedures, triggers are code that runs within a database
Not directly called by a user
Executed when a specified data modification takes place (INSERT, UPDATE or DELETE)
Enforces business rules
FOR AFTER: trigger executes after triggering action completes
FOR INSTEAD OF: trigger executes in place of triggering action
By Anil Kumar

32. Relational Databases Transactions
Transaction: a sequence of SQL statements that constitute a logical unit of work
Must adhere to ACID properties
Atomic: All statements execute successfully or all fail
Consistent: Must leave the data in a consistent state when completed
Isolated: Cannot see the modifications made by concurrent transactions
Durable: Must be permanent when complete, even in the event of system failure
By Anil Kumar

33. Relational Databases Concurrency
Isolation levels
Read Uncommitted
Read Committed
Repeatable Read
Serializable
Tradeoffs (concurrency vs. data integrity)
Locking
Ensures transactional integrity/database consistency
Prevents users from seeing “phantom” data
Can result in deadlocks
By Anil Kumar

34. Thank You
By Anil Kumar