1. Introduction to Databases & SQL
1.0 – 1/28/10
CSC 150 Database Applications & Designs using SQL
Covers material in Chapter 1

2. What is a Database?
A collection of logically related computer data organized for rapid search and retrieval of information
We must define our terms
2 hour talk, spend 1 hour defining your terms

3. Where can databases be found?
Ideas?

4. Databases are ubiquitous

5. What is a Relational Database?
Developed by E. F. Codd in 1970
A collection of tables
Tables used to store data
Tables are rows of records
Records contain fields
Tables can be related to other tables through common fields
Can hold vast amounts of data
Thought that it was impractical, couldn’t work on mainframes
Name based on way structured
Uses tables rather than flat files
Other formats: Hierarchical (Yahoo) and Network – Not easy to change
Tables like Excel spreadsheet – Is Excel a database? No, cannot query

6. Why use a Relational Database?
Flexibility
Runs on many platforms
Simplistic
Easy to learn
Supports many simultaneous users
Can support a front end

7. What is a Table? Means of storing data in a relational database
Set of data elements stored in rows and columns
Two dimensional structure

8. Student ID Last Name First Name Major Code 100100 Simpson Homer PT
100200
Flanders
Ned EN
200100
Marjorie AC
400300
Szyslak
Moe MX
Typical RDB table
Note first row is names of columns

9. Parts of a Table
Rows
Columns
Cells
Primary Key

10. Rows Records Data for one object, event, or relationship
All rows contain similar data
Table may have 1,000s of rows
Rows not in a predictable order
Wouldn’t store student info & professor info in the same table

11. Columns Field Each column named Each column has one datatype
Some columns may allow for no data – null (unknown value), some may not
Columns in specific position
2 or more, usually less than 40
Names must match in related tables
Within a table, each column must have a unique name

12. Cell Where one row meets one column
Atomic – single, undividable piece of data – used as whole
Many datatypes
All cells in a column have same datatype
All cells in a row contain data about one object, event, or relationship
Atomic – splitting first and last name – got back to example table
Most tables use only a small number of datatypes

13. Common Datatypes Text (Alphanumeric) Numeric
Character
Word
String (several words)
Code (M/F, S/M/D)
Numeric
Integer
Floating Point
Currency
Date/Time
Null – no value/unknown value
Text can be numbers not used for arithmetic operations – phone number – student id – many primary keys are number fields used as text

14. Primary Key Unique identification for each row
May be single column or more than one column
Noun – Names the object, event, or relationship
Other columns are adjectives
Allows for quick access of table data
Noun – names the object for each row, other columns are adjectives because the provide a description of the object

15. Rules for Primary Key No two rows can have the same primary key
Primary key cannot contain null values
No table can have more than one primary key
Go back to table – what if Last name was the primary key

16. What is the main reasons to store data in a database?
To reduce redundancy
To maintain data integrity
Redundancy – duplication, storing same information in more than one place
A database allows data to be stored in the efficient means
Less space taken up to store data – less chance for error
Integrity – data stored in the database is correct

17. Normalization Used during database design
A step-by-step process used to reduce redundancy
Each step called a “Form”
First Normal Form
Second Normal Form
Third Normal Form
The higher the Form, the lower the data redundancy
Data referred as being in 1st Normal Form, 2nd Normal Form & so on.
Goal is to get data to third normal form

18. What do We Want to do to Data?
View the data
Add new data
Update existing data
Delete obsolete data
Query the data
Jobs a database needs to perform
Need tool program to help - SQL

19. What is SQL? “Structured Query Language”
Developed at IBM in the early 1970’s by Donald Chamberlin and Raymond Boyce
Used to query & manage a relational database
Declarative language
What, not How
English like
Basics are easy to learn
Procedural language – we tell computer how to do something
Declarative language – we tell the computer what we want, & it figures out how to do it

20. Access & Oracle Two of the most prominent database programs
Both use SQL
Both used in textbook
Access does also have a visual query method
Some slight differences in environment – justifications, etc
Oracle – more serious, used by larger businesses