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UNIT 16 DATABASE SYSTEMS

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Principles of database systems

Databases are everywhere colleges, dentists, supermarkets, banks, DVD stores, hospitals, hotels, gyms, - there are many more examples.

Within each of these organisations the following information could be store; customers, sales, products, suppliers, purchasers, Stock, accounts, VAT.

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These databases are organised in such a way that data can be easily entered, stored, edited, deleted and manipulated to support the activities of the organisation.

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Advantages

Easy to userecords are easy to access and

retrievedata can easily be manipulated in

many waysdata can be validated to ensure that it

is accurate when inputeasy to store

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Disadvantages

Database structures must be carefully developed to ensure that they work as efficiently as possible

there are laws that control the use of databases

many people feel that simply too much information is stored about us

the cost of technology can be prohibitive

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Terminology

An object is something that can be designed, selected and manipulated Tables, queries, forms and reports are all examples of objects.

Tables consists of rows and columns, where the row contains a record and the column becomes a record field.

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Buttons

The user should be able to carry out all their tasks from the form.

They can already add a new record and change data in a record.

You should now add a button to the form to let them delete a record.

A button is a type of shortcut that can help the user to work more efficiently. Add a button to delete records.

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Data entry order [tab order]

The tab will automatically guide you around the form

you can change the data entry order study the handout and change the order

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Query structure

Used to interrogate the data in a database. This means filtering and sorting the data to answer questions.

The query uses the data in the table, by searching the information in the fields and applying the chosen criteria.

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Queries - single criteria

Equals = this will check whether data is exactly

Less than [<] this can be used with number

Greater than [>] can also be used for dates, numbers or text.

Not equals - this can be used to find fields that do not match the data.

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You can combine two or more criteria by using AND, OR, NOT, BETWEEN these are known as multiple criteria.

Study your mobile phone database complete activity use a multiple and single criterion.

Queries - multiple criteria

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Queries

Wild Cards – Wild cards can be used when:You do only remember part of the nameWhen you want to find all records which mention a particular name.

A star represents any numbers of characters or numbersA question mark represents one character or number

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Sorting records

You can sort data via the query in design view.

You can also sort data directly in the table.

Simply click on the relevant field and one of the sorting icons. A to[ascending order] or Z to A [descending order]

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Reports

A report is a printed record of data in the database.

There are several benefits of presenting information in a report rather than just viewing the data on-screen.

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Reports

It counts the records in the report and displays the result.

it adds a heading that can be changed by the user.

It adds the date and time.It adds a age number

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Reports Reports are very useful if you wish to share some of the

information in the database with others in a printed format.

Reports can be laid out so they are easy to read and understand

Reports can be used to select and present exactly the data that someone needs rather than everything in the database.

Although reports are intended to be printed as hard copy, they can also be transferred as electronic documents by email.

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Layouts Columnar layout- each record is laid out with the

fields underneath each other. The labels are placed to the left of the data. This layout ideal when there is a lot of data in each record.

Tabular layout - this arranges the data in a table can be used for forms and reports if the amount of data in each record fits comfortably.

Justified layout- this displays data one record at a time. The appearance is a formal boxed style. Which fits neatly across the page, with the labels for each field above the data. It makes efficient use of space.

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Add buttons to link to forms and reports

Improving efficiency - the database should be easy for the user to use. Normally you will have one main form with options that link to other forms.

You can create forms based on any queries you have created you should decided which ones will be useful to the user.

Add buttons to the main form that link to these. Remember a button is a type of shortcut to help the user to work more efficiently.

The user may want to print out the data from one of these forms, so you can add a button that links to the report.