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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 [email protected] 423.439.6958
2 Bailey [email protected] 423.439.6959
3 Laws [email protected] 423.439.6952
4 Tarnoff [email protected] 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
Tom Jensen
403-555-1919
403-555-1313
Ray Smith 403-555-1919
403-555-1111
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 [email protected]
Mike Hillyer 403-555-1919 [email protected]
Tom Jensen 403-555-1919 [email protected]
Tom Jensen 403-555-1313 [email protected]
Ray Smith 403-555-1919 [email protected]
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
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
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
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
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
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
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
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
