advanced web 2012 lecture 3 sean costain 2012. what is a database? sean costain 2012 a database is a...

Sean Costain 2012

Advanced Web2012

Lecture 3

Sean Costain 2012

What is a Database?A database is a structured way of dealing with structured information.

• An organized mechanism for storing, managing and retrieving information.• Information is stored in tables• Think of a table as a single spreadsheet, a database consists of multiple

spreadsheets that can be linked together using a key.

Sean Costain 2012

Types of Data - Numeric

Tinyint – Use as a boolean

Int – Use for uid/id number

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Types of Data – Numeric cont.

Fixed Point – Decimal, Numeric- Use decimal as numeric defaults to decimal- eg: salary DECIMAL (5,2)Allows for the range -999.99 to 999.99

Floating Point – float, double- Use float- eg: salary FLOAT (7,4)Allows for the range -999.9999 to 999.9999Floating point rounds numbers, so not exact for storage, stick to using decimal.

Sean Costain 2012

Types of Data – Date and Time

DATETIME has a supported range is '1000-01-01 00:00:00' to'9999-12-31 23:59:59'.

TIMESTAMP has a range of'1970-01-01 00:00:01' UTC to '2038-01-19 03:14:07' UTC.

The DATETIME and TIMESTAMP type is used for values that contain both date and time parts.

MySQL retrieves and displays DATETIME & TIMESTAMP values in 'YYYY-MM-DD HH:MM:SS' format.

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Types of Data – StringsString Types

- Char- VarChar- Binary- Varbinary- Blob- Text- Enum- Set

The useful String types

- Varchar- Blob- Text

A varchar can have a set length, eg: varchar(4) means that the field being entered can contain exactly 4 characters. Useful for storing simple data like, M/F, names varchar (60)….

Sean Costain 2012

Types of Data – Strings

Blobs- Tinyblob- Blob- Mediumblob- Longblob

BLOB values are treated as binary strings (byte strings).

They have no character set, and sorting and comparison

are based on the numeric values of the bytes in column

values.Blobs can store images

Sean Costain 2012

Types of Data – Strings

Text- Tinytext- Text- Mediumtext- Longtext

TEXT values are treated as nonbinary strings (character

strings). They have a character set, and values are sorted

and compared based on the collation of the character

set.Text stores … text! (strings)

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Types of Data – Size

Sean Costain 2012

Normalisation

Normalisation Rules• 1st Normal Form

• Eliminate repeating groups• Create a table for related data• Identify each table with a primary key

• 2nd Normal Form• Create tables for sets of values that apply to multiple records• Relate these tables with a foreign key

• 3rd Normal Form• Eliminate fields that do not depend on the key

Normalization is the process of organizing data in a database. This includes creating tables and establishing relationships between those tables according to rules designed both to protect the data and to make the database more flexible by eliminating redundancy and inconsistent dependency.

Sean Costain 2012

Normalisation ExampleSimple spreadsheet that contains student detail.

It works, but sorting by student name or subject would be pretty insane, so we need to normalise the information for storing into a database.

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Normalisation Example Cont.Normalisation on data, break it down and add unique identifiers (uid or id)

So this is the first breakdown of the data, but it’s not broken down enough yet

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Normalisation Example Cont.The address can be broken down further

There has to be links to keep the data consistent

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Normalisation Example Cont.Table linking – Student to address

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Normalisation Example Cont.Table linking – Subject to Date

Though a good break down, reality

doesn’t always fall into 3 rd Normal

form, so you can break the rules.

Sean Costain 2012

Normalisation Example Cont.Table linking – Add Student to Subject and Date

Sean Costain 2012

ERD – Entity Relationship Diagram

Links the tables by Headers

Sean Costain 2012

ERD – Entity Relationship Diagram

All of the tables shown with linking

Sean Costain 2012

phpmyAdmin

Creating a Database- Make a user with the correct privileges- Create a database- Add tables to database- Insert data to tables

Start by having the web server running, get to the web control via- localhost/phpmyadmin

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Creating a userPrivileges- Add User

Sean Costain 2012

Fill in the BlanksWebservers recognise themselves as localhost

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Create Database

Start Adding tables

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Database Fields

Fill in the blanks, such as name, type if it’s auto incrementing and a primary key

Sean Costain 2012

Database

You should end up with multiple tables for your database