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Exam Revision Booklet

Unit 7 (6957)

May 2016

Name: ___________________________

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Contents

Database basics .................................................................................................................................................. 3

Normalisation ..................................................................................................................................................... 5

Data Validation ................................................................................................................................................... 8

Using Naming Conventions ........................................................................................................................... 10

Some questions ................................................................................................................................................ 13

Exam crib sheets .............................................................................................................................................. 14

Making ‘Append’ Queries .......................................................................................................................... 15

Making Macros.............................................................................................................................................. 16

Creating a Query for a report… ................................................................................................................ 17

Other useful things from past papers: ................................................................................................... 18

10 Steps to the stars – PiXl Therapy ............................................................................................................ 19

Exam Technique ............................................................................................................................................... 24

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Database basics

Data is stored in a database so that it can be sorted and searched to provide meaningful

information

What are the advantages of RDBMS over flat file systems?

Recall the main problems of flat file databases

Redundancy

Inconsistency

Difficult to update

Program/data dependence

The aim of using a RDBMS is to eliminate (as far as possible) these problems

Entities:

A relational database consists of multiple

tables joined (linked) together by

relationships

Each table should contain data about a

single entity

Person – Employee

Object - Book

Event - Project

Relationships

Usually joined on primary/foreign key

Relationship have a degree (i.e. there are different types):

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Normalisation

Normalisation made simple (hopefully)

a) 1NF - is to remove repeating groups of data. b) 2NF – is to remove part key dependents, the data that is partly dependent on a key. c) 3NF – is to remove non key dependences, data that is not dependent on other keys

The example below shows a customer order form and how to normalise the data that is on the

form.

Customer No

Customer Name

Customer Address

Order No

Order date

Product No Product

Description

Quantity Price Value

Total

Here is the data structure from the order form in its unnormalised form

Order No

Customer No

Customer Name

Customer Address

Order date

Product No

Product description

Quantity

Price

Value

Total

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Step 1. Remove repeating groups to achieve 1NF.

Note. A repeating group data structure always has a compound key.

1NF. Remove repeating groups.

(1st box) (2nd box)

Order No

Customer No

Customer Name

Customer Address

Order Date

Order No

Product No

Product

Description

Quantity

Price

Value

Step 2. Examine the repeating group data structure and check whether any data item in its

primarily dependent on (solely) the second fields of the compound key. (i.e. any partial key

dependencies?). if such dependences exist, extract these data items to a separate data

structure with their appropriate key field.

The data will now be in 2NF

2NF. Check whether any data item is primarily dependent on (solely) the second fields of the

compound key. (Any part key dependencies)

(2nd box)

Order No

Product No

Product Description

Quantity

Price

Value

Now becomes>>> Order No

Product No

Quantity

Value

Product No

Product Description

Price

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Step 3. Are any of the attributes primarily dependent on one of the other non-key attributes

rather than the design key?

These data structures should now be in 3NF

This stage will involve a foreign key in one of the entities

3NF. Are any of the attributes primarily dependent on one of the other non-key attributes

rather than the design key?

(1st box)

Order No

Customer No

Customer Name

Customer Address

Order Date

Now becomes>>> Order No

Customer No*

Order Date

Customer No

Customer Name

Customer Address

*Foreign key

We can now see that CustomerName and CustmerAddress is primarily dependent on

CustomerNo rather than OrderNo. In this case ant such data items are extracted to a separate

data structure with the appropriate key field.

In order to relate the second structure to the first, the key of the second structure

(CustomerNo) is also left as part of the original structure 9referred to as a ‘foreign key’).

Also at this step, any redundant data is removed e.g. fields which can be calculated. (Value and

Total in this example).

The data is now in 3NF

Customer No

Customer Name

Customer Address

Order No

Customer No*

Order Date

Order No

Product No

Product No

Product Description

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Data Validation Type Description Use

Text Use for text or combinations of text and numbers, such as addresses, or for numbers that do not require calculations, such as phone numbers, part numbers, or postal codes.

Stores up to 255 characters. The FieldSize property controls the maximum number of characters that can be entered.

Memo

Use for lengthy text and numbers, such as notes or descriptions.

Stores up to 65,536 character

Number

Use for data to be included in mathematical calculations, except calculations involving money (use Currency type).

Stores 1, 2, 4, or 8 bytes; stores 16 bytes for Replication ID (GUID). The FieldSize property defines the specific Number type.

Date/Time Use for dates and times.

Stores 8 bytes

Currency Use for currency values and to prevent rounding off during calculations.

Stores 8 bytes.

AutoNumber

Use for unique sequential (incrementing by 1) or random numbers that are automatically inserted when a record is added.

Stores 4 bytes; stores 16 bytes for Replication ID (GUID).

Yes/No

Use for data that can be only one of two possible values, such as Yes/No, True/False, On/Off. Null values are not allowed.

Stores 1 bit

OLE Object

Use for OLE objects (such as Microsoft Word documents, Microsoft Excel spreadsheets, pictures, sounds, or other binary data) that were created in other programs using the OLE protocol.

Stores up to 1 gigabyte (limited by disk space).

Hyperlink Use for hyperlinks. A hyperlink can be a UNC path or a URL.

Stores up to 64,000 characters

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Key Word(s) Answer

Database

Import

Form

Record

Field

Relational database

Flat file database

Data entry and Data entry form

Query

Report

Entities

Attributes

Relationships

Validisation

Presence check

Range check

File lookup check

List check

Format check

Data lengthy check

Input masks

Option buttons

Command buttons

Macros

Normalisation

First Normal form

Second Normal Form

Third Normal Form

What are the main field types?

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Using Naming Conventions

Using naming conventions will make your database easier to create and maintain and could earn you extra marks in your project. Below shows a list of Leszynskil/Reddick naming conventions: Object Naming Convention

Table tbl

Query qry

Form frm

Report Rpt

Macro mcr

Table (lookup) tlkp

Query (select) qry

Query (append) qapp

Query (crosstab) qxtb

Query (delete) qdel

Query (update) qupd

Form (menu) fmnu

Form (message) fmsg

Form (subform) fsub

Macro (menu) mmnu

Input Masks

0: indicates numeric data, entry required

9: indicates numeric data, entry optional

L: indicates alphabetic data, entry required

?: indicates alphabetic data, entry optional

>: forces uppercase

<: forces lowercase

Example: tblClient

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Database Naming Conventions

We need to make sure we use ‘Standard Ways of Working’. In access you have to save each

section of your work.

Add in the correct tag in the table below

Object Tag Example

Table _ _ _ Customer

Query _ _ _ ClientName

Form _ _ _ Customer

Report _ _ _ Sales

Macro _ _ _ UpdateList

Module _ _ _ IsNotLoaded

We also need to make sure we use the correct data types.

Data Type Usage Comments

Text A field can have up to 255 characters

Number Can choose a whole number or a number with a decimal point

Date/Time Access can calculate with dates so never use text to enter dates.

Currency

Yes/No Useful when there are only two possible answers

Auto Number

This is a unique number

Memo Can hold up to 64, 000 characters.

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Some questions

1. In terms of database design, what is a ‘Functional Specification’? [2]

2. List two advantages of the ‘functional specification’ document. [4]

3. With regards to databases, list three examples of ‘Input’. (use any database scenario to describe your answer). [3]

4. With regards to databases, list three examples of ‘Output’. (use any database scenario to describe your answer). [3]

5. With regards to databases, list three examples of a ‘Process’ (use any database scenario to describe your answer). [3]

6. Thinking about a secondary school database system, what could be an example of a ‘generated’ piece of data? Be as descriptive as possible in your answer. [2]

7. What does HCI stand for? [1]

8. With regards to databases, what three factors would you consider to be important when designing a good front-end interface? [6]

9. Describe what a prototype is, in terms of database technology. [2]

10. What are the main advantages of creating a prototype? [3]

11. Why is it important to include a ‘testing’ phase in any large scale database implementation programme? [2]

12. Explain why an ERD may help in the database ‘design’ stage. [2]

13. What does ERD stand for? [1]

14. Explain the downfalls of a ‘many-to-many’ relationship within database systems.

[3]

15. How could a database administrator rectify a ‘many-to-many’ relationship, in order to minimise data replication and potential data loss? [3]

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Exam crib sheets

Creating ‘New Student Form’ and generating StudentID.

To do the above, use the Expression builder, by click on the icon in the

properties / Events pane, of any object.

Remember to ‘unbound’

text boxes.

Set enabled to ‘NO’ on

this box.

Take the 1st character of

the Surname field. (taken

from the Left of the work)

Take the 1st character of

the Forename field.

(taken from the Left of

the work)

Take largest (Max)

number from the right

hand characters of

StudentID (4 from the

right), and then ADD 1.

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Making ‘Append’ Queries

Remember to click the Append Button and select the table you want the information on the

Form you created, to ‘append’ to. (I.e. when you type information on the form, where do you

want it to go in the table?)

Click the Append Button

Right-click ‘Build’

to choose your

Form fields.

Choose the field in

the table you want

to append to.

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Making Macros

To make your form work, you will need to assign your Macro (saved) to a Button you have

drawn on your form. (Design View)

Use the expression builder

to select Form fields and

add Is Null

Use ‘MessageBox’ to

display a message IF the

above statement is true.

If it is NOT true (i.e. the

fields are filled in), do

everything in the ELSE

section.

Draw button

Select button

On Click – set

to your

Macro

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Creating a Query for a report…

With OR, Pseudo column names and Max / Min functions.

Click Totals in order to

to be able to do SUM,

MIN, MAX, and other

functions.

Use AND, OR etc. in this

row, to find specific

criteria.

Use TOTAL row to

include Min / Max /

Sum of columns.

Put a colon : after a

word, to make this the

field title.

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Other useful things from past papers:

Making reports

Force new page, if you

need to print each

record on a new page. Remember to create

sections when you do

reports.

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10 Steps to the stars – PiXl Therapy

I can explain the importance of consistency of data in a database and ways to ensure this. In order to achieve an A*, you have to be able to not only create complex relational databases for your controlled assessment but also be able to explain their uses in the exam. You must also be confident in the different uses of validation, verification and interrogating databases to extract the necessary information. Here are some generic questions that you should be asking as you read a text:

What is a flat file database? What is a relational database? Why do we use relational databases over flat file databases? How can we ensure that the data entered into our database is the correct type

and accurate? How can we interrogate (search) databases to get the information we want?

Relational Databases TASK 1: Ask pupils to define a flat file database and a relational database in no more than 30 words. Share the definitions amongst the group. Can pupils come up with any

possible advantages and disadvantages of using each type of database? TASK 2: Consider the image of the following flat file database. Label the following and explain what data types you would use for each field. Keywords: Table, record, field.

Data types: Text, Numbers, Date/Time, Currency, Autonumber, Yes/No Work with a partner to identify what the other data types could be used for?

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TASK 3: A relational database stores data in tables that are linked together using common fields. Consider the following relational database. As a group, explain how it would provide the following advantages.

Reduces the duplication of data

Ensures that data is up to date

Reduces file sizes.

Ensure that data is consistent

Validation and Verification TASK 4: What is valid data? Why is it so important for a database to have valid data? To ensure that we get valid data, we use validation rules in our database. These make sure that data entered is correct and fit for purpose.

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Match up the following validation rules to their definitions and images.

Validation Rule Definition Example

Length Checks Checks to see if data entered fits within a certain range e.g. between two numbers.

<= 10

Format Checks Checks that data has been entered and not left blank. Often shown by a *.

Field Size: 14

Range Checks Set the field size to only accept the necessary number of characters.

Required: No

Presence Checks Only allows certain types of data to be entered.

Format: Currency

You must learn these examples and definitions. TASK 5: You are creating a database about people at an 18 certificate film.

• What validation rule could you apply to the date of birth field to ensure that you get the correct information?

• What other data validation rules might you include in your database? Why? TASK 6: Data verification is the process of checking that data matches what it was originally. Write your own definitions of the following data verification methods.

Double Entry

Proof reading

*This is something you must do in your exam!

TASK 7: Explain the difference, using examples, between data validation and data verification.

Queries TASK 8: Queries are an extremely powerful tool for searching and sorting information in related databases. They allow the user to search through (sometimes millions) of records instantaneously and get the required information. It is likely that you will have created queries in your controlled assessments.

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Basic Queries usually involved searching one field for specific information. Imagine I have a database of your ICT class.

I want to see how well girls do in the subject. What criteria would I have to include in the gender field of my query?

TASK 9: Complex queries are very powerful tools to search for more than one criterion. For example, if I wanted to find all the girls who scored a grade C or B in their assessment, I would use more than one criterion. Match the following logical operators to their function. Then write an example for the database above.

Logical Operator

Definition Example

AND Searches for one thing OR another.

OR Searches for one thing AND another thing.

NOT Searches for anything that is NOT a specified criterion.

See more query codes here http://tinyurl.com/d97rvyu Imagine I added a column for the age of your classmates.

Ascending is……

Descending is…..

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Relational operators are similar to the signs you will have seen in maths.

= < > <= >=

Which operator would you use if you wanted to:

Find all the students whose age was 14?

Who were older than 14?

Who were younger than 15?

Who were older than or equal to 14?

What do the examiners say about this topic?

Students struggle to identify the difference between records and fields.

Students struggle to identify the primary key and state its function.

Students struggle to identify the advantages of using relational databases over flat file databases.

Many students do not understanding data validation or data verification (name 2 or more techniques) and cannot give examples of each or where they are best applied. Students could not clearly identify the advantages of the different techniques for data validation and verification.

What keywords do you need to know? Before students complete this table, play a game of backs to the board. A student sits in a hot seat and a word is put on the board behind them. Other students have to describe the word without using any of the words that are included in the phrase.

Primary Key

Field

Record

Data Redundancy

Data Duplication

Data Validation

Data Verification

Length Check

Range Check

Format Check

Presence Check

Ascending

Descending

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Exam Technique

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