Relational Database Systems

Higher Information Systems

Advanced Implementation in MySQL/PHP

Developing a solution

Tables Queries User Views Navigation

Introducing SQL

Relational database management systems (RDBMSs) are based on a data definition language called Structured Query Language or SQL (often pronounced “sequel”).

MySQL takes its name from SQL.

Introducing SQL

SQL is a data definition language CREATE DATABASE `DVD Rentals` CREATE TABLE Member(

`Member Number` integer, Name varchar(30), Address varchar(50), `Post Code` varchar(7), `Telephone Number` varchar(11))

Introducing SQL

SQL is also a data manipulation language INSERT INTO Member

VALUES (`233`, `Jo Soap`, `1 Getting Close`, `IS99 2QZ`, `123456`)

SELECT * FROM MemberWHERE `Member Number` BETWEEN 1 and 250ORDER BY `Member Number` DESC

DELETE FROM MemberWHERE `Member Number` > 500

phpMyAdmin

A graphical user interface for MySQL

phpMyAdmin

Viewing a table definition

phpMyAdmin

Adding a record

phpMyAdmin

Selecting records

phpMyAdmin

Viewing selected records

phpMyAdmin

Viewing selected records

Referential Integrity For the database to work properly, it is

essential to guarantee that a foreign key always refers to a record which exists in the other table.

This is called referential integrity. For example, an entry in the Loan table

can only refer to an existing record in the Member table, because a loan can only be made by a member.

Referential Integrity MySQL has no internal facility to maintain

referential integrity (with the default MyISAM table type) - instead, the database’s interface must be designed in such a way that a check is made on any value entered to ensure it is valid.

Usually this is done by using a list on a web page to display the available choices for a field value from which the user may make a selection.

Validation: Presence Check

Validation: Range Check

Range checking is performed by the interface

Use PHP scripting to check numeric values

Validation: Restricted Choice Check

Validation: Default Value

Formatting

All formatting of data for output is done using PHP functions e.g. printf

Queries

Searching Sorting Calculations All searching, sorting and

calculation queries are performed using an SQL expression string

Searching Searching is the process of selecting

records from a table or combination of tables.

To perform the query, three items must be identified:

Which fields will be used to identify the records required?

Which tables are required to produce the data required?

What are the criteria for identifying the records required?

Search 1: Single Condition

Identify the names and telephone numbers of club members with Member Number over 1000

SELECT FORENAME, SURNAME, `TELEPHONE NUMBER` FROM MEMBER WHERE `MEMBER NUMBER` > 1000

Search 1: Single Condition

The asterisk * symbol can be used in an expression string to extract all fields from a table

SELECT * FROM MEMBER WHERE `MEMBER NUMBER` > 1000

Search 2: Multiple Conditions (AND) Identify the names and telephone

numbers of club members with Surnames beginning with M and Member Number over 1000

SELECT FORENAME, SURNAME, `TELEPHONE NUMBER` FROM MEMBER WHERE SURNAME LIKE “M*” AND `MEMBER NUMBER` > 1000

Search 3: Multiple Conditions (OR)

Identify the names and telephone numbers of club members with Surnames beginning with M or N

SELECT FORENAME, SURNAME, `TELEPHONE NUMBER` FROM MEMBER WHERE SURNAME LIKE “M*” OR SURNAME LIKE “N*”

Search 4: More than one table

Identify the names of club members who rented a DVD in August 2005

In order to extract the related records from each table, a join operation is performed in SQL

This will combine those records from each table which have a corresponding record in the other table into a single set of related records (called an answer set)

The keyword used to perform this is INNER JOIN

Search 4: More than one table Identify the names of club members

who rented a DVD in August 2005 SELECT FORENAME, SURNAME, `DATE

HIRED` FROM (MEMBER INNER JOIN LOAN) ON `MEMBER.MEMBER NUMBER`=`LOAN.MEMBER NUMBER`WHERE `DATE HIRED` LIKE “*/8/2005”

Search 5: More than two tables

Identify the names of members who have rented “Shrek”

This time all four tables are required: Member, Loan, DVD and Film.

A nested INNER JOIN statement must be performed to combine these together into a single answer set

Search 5: More than two tables Identify the names of members who have

rented “Shrek” SELECT `FORENAME`, `SURNAME`, `TITLE`

FROM (((MEMBER INNER JOIN LOAN ON MEMBER.MEMBER NUMBER=LOAN.MEMBER NUMBER) INNER JOIN DVD ON LOAN.DVD CODE = DVD.DVD CODE)INNER JOIN FILM ON DVD.FILM CODE = FILM.FILM CODE)WHERE `TITLE` = “SHREK”

Search 6: Dealing with duplicates List those members who have rented

“Shrek” or “Finding Nemo” SELECT `FORENAME`, `SURNAME`, `TITLE`

FROM (((MEMBER INNER JOIN LOAN ON MEMBER.MEMBER NUMBER=LOAN.MEMBER NUMBER) INNER JOIN DVD ON LOAN.DVD CODE = DVD.DVD CODE)INNER JOIN FILM ON DVD.FILM CODE = FILM.FILM CODE)WHERE `TITLE` = “SHREK” OR `TITLE` = “FINDING NEMO”

Search 6: Dealing with duplicates The Group By option is used to eliminate

duplicate results SELECT `FORENAME`, `SURNAME`, `TITLE`

FROM (((MEMBER INNER JOIN LOAN ON MEMBER.MEMBER NUMBER=LOAN.MEMBER NUMBER)

INNER JOIN DVD ON LOAN.DVD CODE = DVD.DVD CODE)INNER JOIN FILM ON DVD.FILM CODE = FILM.FILM CODE)WHERE `TITLE` = “SHREK” OR `TITLE` = “FINDING NEMO”GROUP BY *

Sorting

To perform a sort, two items must be identified: Which field (or fields) will be used to

decide the order of records? For each field selected, will the order

of sorting be ascending or descending?

Sorting To produce a list of people with the

tallest first, the records would be sorted in descending order of height.

To produce a list of people with youngest first, the records would be sorted in ascending order of age.

A very common way of ordering records relating to people is in alphabetical order. To achieve alphabetical ordering requires the records to be sorted in ascending order of surname.

Complex Sorting A complex sort involves more than one

sort condition involving two or more fields.

To achieve “telephone book order”, the name is sorted in ascending order of surname, then ascending order of forename. In this case, the Surname field is the primary sort key, and the Forename field is the secondary sort key.

Sorting

SELECT FORENAME, SURNAMEFROM MEMBER WHERE `MEMBER NUMBER` > 1000ORDER BY SURNAME, FORENAME

SELECT FORENAME, SURNAMEFROM MEMBER WHERE `MEMBER NUMBER` > 1000ORDER BY `MEMBER NUMBER` DESC

Calculations

Horizontal calculations are often known as calculated fields, and vertical calculations are known as summary fields.

Functions (MySQL)

Functions (PHP)

Working with Dates to search for all DVDs rented in the last

week, you would use the expression SELECT * FROM LOAN WHERE

DATEDIFF(CURDATE(),`DATE HIRED`) < 7 to calculate a person’s age in years

from their date of birth, you would use the expression SELECT (YEAR(CURDATE()) – YEAR(`DATE

OF BIRTH`) – (RIGHT(CURDATE(),5)<RIGHT(`DATE OF BIRTH`,5)) AS AGE

Parameterised Queries

User Views User views are created using forms and

reports. A form or report is usually based on a

query which selects the required fields from the appropriate tables, sorting the results if necessary, and performing any horizontal calculations.

In a MySQL application, all output is generally in the form of a web page.

Report Structure

Summary Information Sum to add values to give a total, e.g.

Total Cost of DVD Rentals last month Average to find an average value, e.g.

Average Cost of Hire per DVD Count to count the number of records

found, e.g. Number of DVDs rented per member

Maximum to find the highest value, e.g. Highest number of rentals per DVD

(to find the most popular DVD) Minimum to find the lowest value, e.g.

Lowest number of rentals per member

Summary Information In a MySQL application, the aggregate

functions SUM, AVG, COUNT, MAX and MIN can be used in an SQL expression string to produce summary information for a set of extracted records

However, certain summary information, such as page totals, would have to be programmed using PHP (e.g. counting the number of records being displayed)

Scripting In a MySQL application, all navigation

and user interface features are implemented using scripting

$result = @mysql_query("SELECT Forename, Surname FROM Member");

while ( $row = mysql_fetch_array($result) ) { $forename = $row["Forename"]; $surname = $row["Surname"]; echo("<tr><td>$forename</td><td>$surname</td></tr>");

}

Macros