Phil Smith

Learning outcomes LO2

LO2 Develop a fully functional relational database system, based on an existing system design.

The design for the assessment is of your own choosing.

Implementation of security elements in databases.

Relational databases with controls like data validation using; input masks,

drop down lists, option buttons.

User interface for requirements, functionality, reliability, consistency and

performance.

Implementation – DQL1. DQL: Data Query Language

Sample activities:

Demonstration of query language and application by

students to apply to own applications.

Implementation – DQL1. TASK

Firstly we need another example of the MWS

database.

On your local xampp.

Create a new database name emws.

Import emws.sql on studshare/HND

We shall use emws for the web based interface.

SQL - Select

The SELECT clause is use to make queries against

data held in one or more tables in your database.

The basic syntax of the select clause -

SELECT column-name1, column-name2, column-name3, column-nameN

from table-name;

SQL: SELECT Statement

A basic SELECT statement includes 3 clauses

SELECT <attribute name> FROM <tables> WHERE <condition>

SELECT

Specifies the

attributes that are

part of the resulting

relation

FROM

Specifies the tables

that serve as the

input to the

statement

WHERE

Specifies the

selection condition,

including the join

condition.

Note: that you don't need to use WHERE

Using a “*” in a select statement indicates that

every attribute of the input table is to be selected.

Example: SELECT * FROM … WHERE …;

To get unique rows, type the keyword DISTINCT

after SELECT.

Example: SELECT DISTINCT * FROM …

WHERE …;

SQL: SELECT Statement (cont.)

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SELECT Statement Clauses of the SELECT statement:

SELECT

List the columns (and expressions) that should be returned from the query

FROM

Indicate the table(s) or view(s) from which data will be obtained

WHERE

Indicate the conditions under which a row will be included in the result

GROUP BY

Indicate columns to group the results

HAVING

Indicate the conditions under which a group will be included

ORDER BY

Sorts the result according to specified columns

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Figure 7-8: SQL statement

processing order

SELECT Example 1 List Customers

We have already done this single table query.

SELECT `Title`,`FirstName`,`Surname`,`DateOfBirth`

FROM `customer`

SELECT Example 2 List Customers

We have already done this multi table query.

SELECT `Title`,`FirstName`,`Surname`,`DateOfBirth`,

orders.DateOfOrder

FROM `customer`

Inner Join orders on orders.CustomerID =

customer.CustomerID

SELECT Example 3 List Customers

We have already done this multi table query. Only Customers who have placed orders whose first name is Jean?

SELECT `Title`,`FirstName`,`Surname`,`DateOfBirth`, orders.DateOfOrder

FROM `customer`

Inner Join orders on orders.CustomerID = customer.CustomerID

Where Firstname = “Jean”

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SELECT Example using Alias Alias is an alternative column or table name

SELECT CONCAT(CUST.Firstname, ' ',

CUST.FirstName) AS NAME, CUST.City

FROM CUSTOMER CUST WHERE

`Surname` = "Jones"

Using a Function Using the COUNT aggregate function to find totals

Aggregate functions: SUM(), MIN(), MAX(), AVG(),

COUNT()

How many customers do we have?

SELECT Count(*) FROM `CUSTOMER`

Answer = 44 in the MWS example data

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SELECT Example – Boolean Operators

AND, OR, and NOT Operators for customizing

conditions in WHERE clause

SELECT phones.Model, designs.DesignType, designs.Cost

FROM `products`

Inner join phones on phones.id = products.PhoneID and

phones.Model = 'iPhone 7'

Inner join designs on designs.id = products.DesignID

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SELECT Example – Like

SELECT phones.Model, designs.DesignType, designs.Cost

FROM `products`

Inner join phones on phones.id = products.PhoneID

Inner join designs on designs.id = products.DesignID

Where phones.Model LIKE "%iP%"

Note: the LIKE operator allows you to compare strings using

wildcards. For example, the % wildcard in ‘%Desk’ indicates that all

strings that have any number of characters preceding the word “Desk”

will be allowed

SELECT Example –Sorting Results with the ORDER BY Clause

Sort the results first by Design

SELECT phones.Model, designs.DesignType, designs.Cost

FROM `products`

Inner join phones on phones.id = products.PhoneID

Inner join designs on designs.id = products.DesignID

Where phones.Model LIKE "%iP%"

Order by designs.DesignType

SELECT Example –with the in Clause

Inclide results where city is in a provided list

SELECT * FROM `customer` WHERE `City` in ("Hereford",

"Molden")

Note: the IN City value is either Hereford or Molden. It is more efficient

than separate OR conditions

SELECT Example –Categorizing Results Using the GROUP BY Clause

SELECT City, Count(*) FROM `customer`

Group By City

Note: you can use single-value fields with aggregate

functions if they are included in the GROUP BY clause

SELECT Example –Qualifying Results by Categories Using the HAVING Clause

For use generally with GROUP BY

SELECT phones.Model, designs.DesignType,

designs.Cost FROM `products`

Inner join phones on phones.id = products.PhoneID

Inner join designs on designs.id = products.DesignID

Having designs.Cost > 3.50

Like a WHERE clause, but it operates on groups (categories),

not on individual rows. Here, only those groups with total

numbers greater than 1 will be included in final result

Using and Defining Views

Views provide users controlled access to tables

Base Table – table containing the raw data

Dynamic View A “virtual table” created dynamically upon request by a user

No data actually stored; instead data from base table made available to user

Based on SQL SELECT statement on base tables or other views

Sample CREATE VIEWCREATE VIEW `viewshowusers` AS

select `users`.`userid` AS `userid`,`users`.`userlogin` AS `userlogin`,`users`.`firstnames` AS `firstnames`,`users`.`surname` AS `surname`,`users`.`adminuser` AS `adminuser`

from `users` ;

▪View has a name

▪View is based on a SELECT statement

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Advantages of Views

Simplify query commands

Assist with data security (but don't rely on views for security, there are more important security measures)

Enhance programming productivity

Contain most current base table data

Use little storage space

Provide customized view for user

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Disadvantages of Views

Use processing time each time view is referenced

May or may not be directly updateable

SQL: Join operation

A join can be specified in the FROM clause

which list the two input relations and the

WHERE clause which lists the join condition.

Example:

Biotech1003

Sales1002

IT1001

DivisionID

TN1002

MA1001

CA1000

StateID

Emp Dept

SQL: Join operation (cont.)

Sales1002

IT1001

Dept.DivisionDept.ID

TN1002

MA1001

Emp.StateEmp.ID

inner join = join

SELECT *

FROM emp join dept (or FROM emp, dept)

on emp.id = dept.id;

SQL: Join operation (cont.)

IT1001

Sales1002

nullnull

Dept.DivisionDept.ID

CA1000

TN1002

MA1001

Emp.StateEmp.ID

left outer join = left join

SELECT *

FROM emp left join dept

on emp.id = dept.id;

SQL: Join operation (cont.)

Sales1002

Biotech1003

IT1001

Dept.DivisionDept.ID

MA1001

nullnull

TN1002

Emp.StateEmp.ID

right outer join = right join

SELECT *

FROM emp right join dept

on emp.id = dept.id;

SQL Union1. You can combine the output from two or more

queries/views by using the union clause.

2. The general form is -

Select col1, col2 from table1 where col1 = ‘xxx’

Union

Select col3, col4 from table2 where col3 = ‘yyy’

Rules, the selected columns from each query must

match in type, the output column must be the same

type.

SQL Correlated sub queryConsider this query - we want to list all customers who have placed no orders.

We could try and do this with left outer joins.

But we can to a correlated subquery.

Select `FirstName`,`Surname` From Customer C

Where not exists (select "a" from orders CO where CO.Customerid = C.Customerid)

The sub query returns a true/false condition.

Select ‘a’ is faster then returning a column.

Implementation – TestingLO3. Test the system against user and system

requirements.

Identify elements of the system that need to be tested.

Consider data that should be used to fully test the

system.

Match tests against user and system requirements.

Test procedures to be used: test plans, test models e.g.

white box, black box;

testing documentation.

Functional and system testing and testing the robustness

of the system,

including help menus, pop-ups, hot-spots, data validation

checks.

Implementation – TestingTesting and test data.

Database Testing is checking –

1. the schema (physical against logical)

2. Tables (structure – keys, validation, defaults etc)

3. Triggers (if any)

4. It may involve creating complex queries to

load/stress test the database

5. check its responsiveness to 5 above.

6. Checks data integrity

7. Check consistency

8. Check insert/update anomalies.

Implementation – Testing

Implementation – Testing

The 3 types of Database Testing are

Structural Testing

Functional Testing

Non-functional Testing

Structural database testingThe structural data testing involves the

validation of all those elements inside the

data repository that are used primarily for

storage of data and which are not allowed to

be directly manipulated by the end users.

The validation of the database servers is

also a very important consideration in these

types of testing.

The successful completion of this phase by

the testers involves mastery in SQL queries.

Schema testingThe structural data testing involves the

validation of all those elements inside the

data repository that are used primarily for

storage of data and which are not allowed to

be directly manipulated by the end users.

The validation of the database servers is

also a very important consideration in these

types of testing.

The successful completion of this phase by

the testers involves mastery in SQL queries.

What have we learnt today?

Applying techniques to your own problem.

You need to create your own database from your

own design.