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MySQLInteract withDatabase

Introduction to MySQL

Relational databases Database design SQL

Creating databases Creating tables Selecting from, deleting, and updating tables

Exercises

You should have Class notes Exercise handout MySQL Pocket Reference

Useful resource: http://dev.mysql.com/doc/

Basics of DatabasesA database is made up of:

fields – a compilation of types of information or properties records – a compilation of individual items with specific

values for the aforementioned information or properties

For example, a student record could contain fields such as student id, name, rank, street address, city, state, and zip code.

A specific record might have a student id of 12345678, name of Jane Smith, rank of sophomore, street address of 9999 Buttermilk Lane, city of Johnson City, state of Tennessee, and a zip code of 37601.

Relational Databases

A database may contain multiple tables too. For example, a database used for a section

of a course may need to have a way to identify a student (student ID), but would not have to the student's personal information

Therefore, the university's database would contain multiple tables: Student information Course information Classroom information

Basics of Databases (continued) All of this information is contained in tables

where the rows represent each record and the columns represent the fields.

First Name Last Name PhoneNadia Li 2687Madhu Charu 7856Ajuma Kinsaka 4489Wade Randal 5257Helen Clark 2147

Employees

Relational Databases

A database is a collection of tables Columns define attributes of the data

All data in a column must have the same data type

A record is stored in a row

table name

column

row

"Hey, a table! That's kinda like a spreadsheet, right?" Unlike a spreadsheet, the rows (records) of a

database must be independent of one another Unlike a spreadsheet, the columns (fields) of a

database should be independent of one another Example: Gradebook with columns for each quiz, test,

and homework grade. Spreadsheet: one column might be used to compute the final

grade Database: Cannot have a field for this. Instead, just before

you presented the data (results set), you would calculate a final grade to be presented. That value is never stored in a table.

Relational Databases (continued)Student Table•ID•Name•Z-account•Rank•Address•Phone number

Instructor Table•ID•Name•E-mail address•Department•Office location•Office phone

Course Table•Course ID•Catalog description•Credit hours•List of topics

Course Section Table•Course•Section number •Instructor•Students

Use a Relational Database When…

You have a very large dataset There is redundant data

Wastes disk space Increases errors

Information must be updated in multiple locations

Security is important Different users can be granted different permissions

Strict enforcement of data types is important

Spreadsheet Example

Title Author Borrower PhoneA House for Mr. Biswas VS Naipaul Sarah 646.555.1234Midnight's Children Salman RushdieOn the Road Jack Kerouac

Spreadsheet Example

Title Author Borrower PhoneA House for Mr. Biswas VS Naipaul Sarah 646.555.1234Midnight's Children Salman RushdieOn the Road Jack Kerouac

Data is inconsistent!

Now imagine you are designing the New York Public Library database which has tens of million books and well over a million cardholders.

One Flew Over the Cuckoo's Nest Ken Kesey Sarah 646.555.1244Sula Toni MorrisonVillette Charlotte Bronte Jim 646.555.4586

Database Design

Entity Relationship Design

Entity (“thing”, “object”) Table

Attributes (describe entity) Columns

Entity Instance Row

Relationships between entities preserved in relationships between tables.

If you are interested in learning more formal design methods look up “normalization” and/or “third normal form”.

Keys

A key is a field by which records may be sorted.

There are a number of uses for keys: A primary key can be used to uniquely identify a

record. A common key is a key shared by two tables in a

relational database. A foreign key is a common key that can be used

to identify records from another table.

Primary Keys Each record within a table must somehow be uniquely

identifiable. For example, how can we make sure that we're looking

at the correct student information in the student table? Answer: No two students share the same student id. Siblings may have the same parents, roommates may

have the same address, but no one has identical student IDs.

Therefore, we can use a field containing the student id to identify a specific record in the student database.

This unique identification is called the Primary Key.

Our tables

• A primary key is a unique identifier for a record in a table.• A foreign key in one table refers to the primary key of another.

Simple Relational Database Example

Department Course Section Semester Year Instructor

CSCI 2800 001 Spring 2006 2

CSCI 2800 201 Spring 2006 1

CSCI 2910 001 Spring 2006 4

CSCI 2910 201 Spring 2006 3

ID Name E-mail Phone

1 Bailes bailes@etsu.edu 423.439.6958

2 Bailey baileyg@etsu.edu 423.439.6959

3 Laws lawsm@etsu.edu 423.439.6952

4 Tarnoff tarnoff@etsu.edu 423.439.6404

Instructor Table

Course Table

Primarykeys

Databases and the Client/Server Model Database systems typically reside on the server, but

are not as part of the software providing server functionality.

An interface must exist between server software and the database.

Three tier architecture – Server/client model adds middle layer that handles transactions between client and database server.

Middle layer provides: ability to access more than one database with a single

transaction ability connect to many different types of data sources ability to prioritize requests before they reach the data base improved security

What is SQL?(Adapted from material found at http://www.atlasindia.com/sql.htm)

Dr. Edgar F. Codd created a model for data storage that used a simple programming language to access the stored data

In 1971, IBM used Dr. Codd's work to created a simple non-procedural language called Structured English Query Language (SEQUEL)

In the late 80's, two standardization organizations (ANSI and ISO) developed a standardized version called Structured Query Language or SQL.

What is SQL? (continued)(Adapted from material found at http://www.atlasindia.com/sql.htm)

SQL is the language used to query all databases. It is a generic way to access the information in a

database. Understanding SQL is vital to creating a

database application such as a web interface.

WebApplication

DatabaseSQL

Different SQL Implementations

There are multiple vendors of database products, each with their own implementation of SQL

Each product should be compliant with ANSI standard

Added features or commands do exists. These are called extensions.

Using SQL Assume that a database structure already

exists, i.e., someone has already created tables for us containing fields and records.

What sort of things might we want to do to this database? Start/end a session with a specific database Read a record Insert a new record Delete an existing record Edit and restore an existing record

Basic SQL Syntax

➔ Data Definition Language (DDL)

• CREATE TABLE / DATABASE / VIEW / etc.....• ALTER ...• DROP ...

➔ Data Manipulation Language (DML)

• SELECT ... FROM / INTO … WHERE ...• INSERT INTO ... VALUES ...• UPDATE … SET … WHERE ...• DELETE FROM … WHERE ...

Querying Records

A query is an inquiry to the database for information. This is done with SELECT.

Syntax:SELECT *| fieldname [, fieldnames] FROM tablename [, tablenames] WHERE fieldname=value ORDER BY fieldname [, fieldnames]

Example:SELECT FirstName FROM Customers WHERE LastName='Smith'

Data Manipulation

There are three basic commands to manipulate data: INSERT DELETE UPDATE

Adding a Record

Syntax:

INSERT INTO tablename (fieldname [, fieldnames]) VALUES (value [, values])

Example:

INSERT INTO Customers (FirstName, LastName) VALUES ('Jane','Smith')

Removing a Record Syntax:

DELETE FROM tablename WHERE fieldname=value

Example:

DELETE FROM Customers WHERE LastName='Jones'

Updating a Record Syntax:

UPDATE tablename SET fieldname=value WHERE fieldname=value

Example:

UPDATE Customers SET FirstName='Jeff' WHERE LastName='Smith'

What Is Database Normalization?

Cures the ‘SpreadSheet Syndrome’ Store only the minimal amount of

information. Remove redundancies. Restructure data.

What are the Benefitsof Database Normalization? Decreased storage requirements! 1 VARCHAR(20) converted to 1 TINYINT UNSIGNED in a table of 1 million rows is a savings of ~20 MB Faster search performance!

Smaller file for table scans. More directed searching.

Improved data integrity!

What are the Normal Forms?

First Normal Form (1NF) Second Normal Form (2NF) Third Normal Form (3NF) Boyce-Codd Normal Form (BCNF) Fourth Normal Form (4NF) Fifth Normal Form (5NF)

Our Table

name phone1 phone2 email1 email2Mike Hillyer

403-555-1717

403-555-1919

mike@hoppen.com

mhillyer@mysite.com

Tom Jensen

403-555-1919

403-555-1313

tom@openwin.org

tom@supersite.org

Ray Smith 403-555-1919

403-555-1111

ray@cpma.com

user

namenicknamephone1phone2phone3cellpageraddresscityprovincepostal_codecountryemail1email2web_urlcompanydepartmentpicturenotesemail_format

First Normal Form

Remove horizontal redundancies No two columns hold the same information No single column holds more than a single

item

Each row must be unique Use a primary key

Benefits Easier to query/sort the data More scalable Each row can be identified for updating

One Solution

first_name last_name phone emailMike Hillyer 403-555-1717 mike@hoppen.com

Mike Hillyer 403-555-1919 mhillyer@mysite.com

Tom Jensen 403-555-1919 tom@openwin.org

Tom Jensen 403-555-1313 tom@supersite.org

Ray Smith 403-555-1919 ray@cpma.com

Ray Smith 403-555-1111

• Multiple rows per user

• Emails are associated with only one other phone

• Hard to Search

user

first_namelast_namenicknamephonecellpageraddresscityprovincepostal_codecountryweb_urldepartmentpicturenotes

Satisfying 1NF

user

PK user_id

first_namelast_namenicknameaddresscityprovincepostal_codecountryweb_urlcompanydepartmentpicturenotes

phone

PK phone_id

country_codenumberextension

email

PK email_id

address

Forming Relationships

Three Forms One to (zero or) One One to (zero or) Many Many to Many

One to One Same Table?

One to Many Place PK of the One in the Many

Many to Many Create a joining table

Joining Tables

user

PK user_id

first_namelast_namenicknameaddresscityprovincepostal_codecountryweb_urlpicturenotesemail_format

email

PK address

FK1 user_id

user_phone

PK,FK1 phone_idPK user_id

type

phone

PK phone_id

country_codenumberextension

user

PK user_id

first_namelast_namenicknameaddresscityprovincepostal_codecountryweb_urlpicturenotesemail_format

email

PK address

FK1 user_id

user_phone

PK,FK1 phone_idPK user_id

type

phone

PK phone_id

country_codenumberextension

Our User Tablefirst_name last_name company departmentMike Hillyer MySQL Documentation

Tom Jensen CPNS Finance

Ray Smith CPNS Documentation

Second Normal Form

Table must be in First Normal Form Remove vertical redundancy

The same value should not repeat across rows

Composite keys All columns in a row must refer to BOTH parts

of the key

Benefits Increased storage efficiency Less data repetition

Satisfying 2NF

email

PK address

typeFK1 user_id

phone

PK phone_id

country_codenumberextensiontype

user

PK user_id

first_namelast_namenicknameaddresscityprovincepostal_codecountryweb_urlpicturenotes

user_phone

PK,FK1 user_idPK,FK2 phone_id

company

PK company_id

name

user_company

PK,FK1 user_idPK,FK2 company_id

department

email

PK address

FK1 user_id

user

PK user_id

first_namelast_namenicknameaddresscityprovincepostal_codecountryweb_urlpicturenotesemail_format

Third Normal Form

Table must be in Second Normal Form If your table is 2NF, there is a good chance it is

3NF

All columns must relate directly to the primary key

Benefits No extraneous data

Satisfying 3NF

email

PK address

FK1 user_idformat

phone

PK phone_id

country_codenumbertype

user

PK user_id

first_namelast_namenicknameaddresscityprovincepostal_codecountryweb_urlpicturenotes

user_phone

PK,FK1 user_idPK,FK2 phone_id

extension

company

PK company_id

name

user_company

PK,FK1 user_idPK,FK2 company_id

department

Finding Balance

email

PK address

FK1 user_idformat

phone

PK phone_id

FK1 type_idarea_codeNXXNCX

FK2 country_id

user

PK user_id

first_namelast_namenicknameunitstreet_numberstreet_namestreet_typequadrantweb_urlpicturenotes

FK1 postal_code

user_phone

PK,FK1 user_idPK,FK2 phone_id

extension

company

PK company_id

name

user_department

PK,FK1 user_idPK,FK2 department_id

type

PK type_id

type

country

PK country_id

Namephone_code

department

PK department_id

nameFK1 company_id

postal_code

PK postal_code

FK1 city_id

province

PK province_id

NameAbbreviation

FK1 country_id

city

PK city_id

nameFK1 province_id

Joining Tables

Two Basic Joins Equi-Join Outer Join (LEFT JOIN)

Equi-Join SELECT user.first_name, user.last_name, email.address FROM user, email WHERE user.user_id = email.user_id

LEFT JOIN SELECT user.first_name, user.last_name, email.address FROM user LEFT JOIN email ON user.user_id = email.user_id

De-Normalizing Tables

Use with caution Normalize first, then de-normalize Use only when you cannot optimize Try temp tables, UNIONs, VIEWs,

subselects first