Human Computer Interaction

Learning Outcomes

On completion of this page you will know how to:

• Create a blank database
• Create a table within that database
• Create fields within that table
• Create key field for the table
• Alter properties of fields such as default values, validation rules, field size etc.

Introduction

For our first application we shall look at a very simple database for the organisation that we referred to in the previous page. The data we shall need will be:

• Employee number
• IRD number
• Full Name
• Commencement Date
• Finishing Date
• Address 1
• Address 2
• Contact Phone
• Hourly Rate
• Tax Rate
• Department
• Current

These items above are the names specified in the previous page

Creating a new Database

Creating a new Access database is like creating any new object using other software such as Word, Excel etc. The steps are:

1. Ensure that Microsoft Access is running
2. Click on File/New. This will give you a display as in Fig 1 below.
3. From Available Templates select Blank Database and in the box labeled File Name enter the name of the database.
4. Click on the button Create.

Our new database now appears as in Fig 2 below

There are many different objects that we can put into a database. These include tables, queries, forms, reports, web pages, macros and programming code. Of those we have examined the concepts of tables very thoroughly in the previous chapter. Here, before actually creating a table we shall take a quick look at queries, forms and reports.

Queries: this is a way of selecting from all of the data stored only the data that we want for a particular application. Queries are extremely useful when we are trying to extract data from more than one table.

Forms: A GUI interface that allows us to look at a table one record at a time. A form will also allow us to enter data into the table.

Reports: Paper printouts of part of the data in the database. Usually they are subtotaled.

Creating a Table

When you create a new database, Access automatically creates a new table for you. If it does not or if you wish to create a second table you simply go to the Create tab and click on the icon Table. Either way you get a display as shown in Fig 2 above. The first thing you must do is to save the table. As we are going to enter employees’ data into this table we shall call it Employees. To save the table, simply right click on the tab that has the table’s name on it. In Fig 2 the table’s name is Table 1. Once you right click a pop up menu appears and among the options is Save. Once you select this option a dialogue box appears asking for the table’s name. Here you enter Employees and then click on OK. Now the name Employees will replace the name Table 1 in the table’s tab.

As your table is newly created it has no fields in it. Your first task therefore is to add fields to the table. To do this, however, you must change the table display to Design View To do this, again right click on the table’s tab, and from the pop-up menu select Design View. This alters the display as shown in Fig 3 below.

Specifying Field Names and Field Types

We are now ready to enter the description of our table, or in other words specify the fields and their characteristics. First in the column Field Name we enter the name of the first field – EmployeeNumber in this case. Once we do this AutoNumber appears automatically in the Data Type column. In this case this is what we want and therefore will not change it.

Finally, we enter a description in the Description column. Strictly speaking, this is not necessary for the normal running of the database. However, screen readers are able to access and read out the contents of this enabling visually impaired and dyslexic people to know the structure of the table. For this reason we shall enter a description for every field of the table. As we already have a conceptual model which describes the fields of the table we can simply copy and paste those descriptions into the different cells of the Description column. Fig 4 below shows part of this description.

Data type

The value AutoNumber was automatically put into the first field of the table and since that is the type we wanted for our EmployeeNumber field we did not alter it. However, any table should have only one AutoNumber field and or the rest of our fields we need to use other data types

Fig 5 shows all of the values that we can give to Data Type. Of those we shall be using Short Text, Number, Date/Time, Currency, AutoNumber and Yes/No. We shall explain each of those values later on as we use them in context.

Below we show a completed table designed according to the conceptual model from the previous chapter.

Using the Caption Property

Notice in Fig 6 that we are using Camel Script for our field names. (Camel Script refers to removing all spaces from a name and using a capital letter to signify the beginning of each word.) The reason for this is that some software applications wont accept spaces in field names of a table or else the field names must be specially formatted for them to be accepted.

However, showing Camel Script in forms or reports don’t look good as viewers would prefer to have captions with words separated by spaces. If we want to keep our Camel Script and at the same time provide users with words separated by spaces, we need to use the Caption property.

Looking at the General tab of Fig 4 one of the properties that have not been given a value is the Caption property. If this was given a value of “Employee Number”, then this would appear on forms, reports etc. instead of the field name.

All other fields, with names of more than one word should have their Caption property updated accordingly.

Design View/Datasheet View

A database table is for holding data entered by the user. So far, however, we have not entered one single item. This is because we have spent the time designing the table and configuring the fields to ensure that the data entered is as correct as possible. What we have seen of the table, therefore, is the Design View. In this view we cannot enter any data, we can only specify the type and range of data that can go into the fields. Since our table is now fully designed, we are ready to start entering data into it. In order to do this, we have to go to another view of the table – the Datasheet View. In order to do this, we right click on the table tab and from the pop up menu select Datasheet View. The table now changes as shown in Fig 7.

Notice that instead of the actual field names appearing above the data in the fields, the values of the Caption properties appear instead.

Summary

A table is a rectangular grid in which data is stored. When a table is designed the fields are defined. This includes the data type that each field will store, the size of the field if its text, default values, validation rules and validation text. A table normally has a primary key. This is a field where duplication of data is not allowed and its contents are used to uniquely identify each record.