1. INFO/CSE 100, Spring 2006 Fluency in Information Technology
Database Intro
INFO/CSE 100, Spring 2006
Fluency in Information Technology
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2. Readings and References
Fluency with Information Technology
Chapter 13, Introduction to Database Concepts
References
Access Database: Design and Programming
by Steve Roman, published by O'Reilly
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3. fit100-23-databases © 2006 University of Washington
Why Study Databases?
Some of us want to compute, but all of us want information …
Much of the archived information is in tables
Databases enhance applications, e.g. Web
Once you know how to create databases, you can use them to personal advantage
Databases introduce interesting ideas
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4. fit100-23-databases © 2006 University of Washington
Relational Databases
Information is stored in tables
Tables store information about entities
Entities have characteristics called attributes
Each row in a table represents a single entity
Each row is a set of attribute values
Every row must be unique, identified by a key
Relationships -- associations among the data values are stored
Table structure = schema Table contents = instance
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5. fit100-23-databases © 2006 University of Washington
A Table in a Database
Tables have names, attributes {fields}, entities {rows}
Schema for Example table:
ID number unique number(Key)
Last text person’s last name
First text person’s first name
JobCode number current position
Hire date first day on job
...
instance
Attributes are sometimes referred to as fields, represented by the columns.
Entities are sometimes referred to as rows or tuples.
The schema is the structure of the table.
schema
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6. Two tables in a database
Tables: Example, JobCodes
Example: 6 rows or entities and 9 fields or attributes, ID is key
JobCodes: 3 rows and 3 fields, JobID is key
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7. Redundancy in a database is Very Bad
Not every assembly of tables is a good database
Repeating data is a bad idea
Replicated data can differ in its different locations, e.g. multiple addresses can differ
Inconsistent data is worse than no data
Cut down on the typos and mis-keyed entries
Keep a single copy of any data
Reduces memory and data processing costs
if it is needed in multiple places, associate it with a key and store key rather than the data
Effort to update is high
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8. Relationships between tables
Relationship between the Perms table and JobCodes table,
They share field JobID.
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9. fit100-23-databases © 2006 University of Washington
“You can look it up”
When looking for information, a single item might be the answer, but a table is more likely
Which employees live in Kirkland?
Table of employees
Who is taking INFO/CSE 100?
Table of students
Whose mile run time  4:00?
Table of runners
A query to a table produces a new table as a result!
Query to a database (set of tables) produces a new table
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10. Relational Algebra: Tables From Tables
There are five basic “algebraic” operations on tables:
Select -- pick rows from a table
Project -- pick columns from a table
Union/Join -- combine two tables w/like columns
Difference -- remove one table from another
Product -- create “all pairs” from two tables
From this basis, many more complicated operations can be built up
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11. fit100-23-databases © 2006 University of Washington
Select Operation
Select creates a table from the rows of another table meeting a criterion
Select_from Example On Hire < 1993
Structured Query Language (SQL) in red
Table in green
Condition {test} in blue
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12. Project Project creates a table from the columns of another table
Project Last, First From Example
This is a projection from 9 dimensions to 2 dimensions
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Union
Union combines two tables with same attributes
All employees = perms UNION temps
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Difference
Difference (written like subtraction) removes 1 table’s rows from another
Eastern = States - WestCoast
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Product
Product (written like multiplication) combines columns and pairs all rows
Colors = Blues x Reds  =
Column Rule: If A has x columns, B has y columns, A x B has x+y columns
Row Rule: If A has m rows, B has n rows A x B has mn rows
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16. Join
Join (written like a bow tie) combines rows if common field matches
Employee List = Perms JobCodes
><
Join is kind of like a Product,, except only combine rows if common fields match!

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DB Operations
The five DB Operations can create any table from a given set of tables
All modern database systems are built on these relational operations
Join is not primitive, but can be built from 5
Join, select and project are used most often
The operations are not usually used directly, but are used indirectly from other languages
Structured Query Language (SQL) is the language that we talk to the database in
SQL, the DB language we learn, is built on basic 5
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18. fit100-23-databases © 2006 University of Washington
Database Structure
A database contains one or more tables
Tables include entities with attributes
There are relationships defined between the entities in the various tables
Retrieve information from the tables using queries
Create GUI front ends (forms and reports) for users
First, design the database or create the schema
What are the entities?
What are the attributes of each entity?
What are the relationships between tables?
Creating a database…
Lets consider all of the details about the database schema first!!!
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19. entity-relationship diagram for Library database
Price
Name
ISBN
Title ID
Phone ∞
WrittenBy ∞
Books
Authors ∞
PublisherOf 1
Publishers
entity-relationship diagram for Library database
Books, Publishers, Authors are tables
Price, ISBN, Title are attributes of the table Books
There is a relationship between Books and Publishers
1 Publisher can have many Books ID
Phone
Name

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Create a new database
We are going to be using MS Access.
Its available on the Lab machines and in MS Office if you have that installed on your home computer already.
Step 1: create a new database , with a .mdb file extension
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21. Create a new table in the database
MS Access tries to be friendly and offer you some choices!
Select "Create table in Design View".
Do not use the Wizard!
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22. Creating a table in Design view
Aha! Now you've got to enter in the attributes {fields} of the table.
Attributes have a field name, data type, and a description.
In this example, three fields are being created: ISBN, Title, and Price.
ISBN field is specified as the key (see key icon). Remember that the key field must be unique!
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Entering Table Data
Once the table has been added you must view leave the Design View to enter data into the table.
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24. fit100-23-databases © 2006 University of Washington
Build another table
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25. Add publisher ID to books
Field properties allow you to add more details about each attribute {field}, including things
like size, format (for dates), number of decimal places, required, etc…
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26. Create the link between the tables
From the Relationships view. We can create a link by dragging a line between
a field from one table to a field on another table.
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27. Hey presto, we have a database!
Price
Name
ISBN
Title ID
Phone ∞
WrittenBy ∞
Books
Authors ∞
PublisherOf 1
Publishers
Hey presto, we have a database! ID
Phone
Name

28. Two tables with a relationship
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Create a query
Create a query in Design View.
Step 1: select query from the object lists.
Step 2: select the tables you want to query from.
Step 3: select the fields you want to query from.
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30. The query produces a new (virtual) table
A query produces a new table, of which we see the results.
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31. Project (select particular columns)
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32. Select particular rows
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33. fit100-23-databases © 2006 University of Washington
SQL behind the scenes
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