Computed Fields in Databases

Computerised databases have an advantage in that computed fields can be created. These fields contain a calculation using one or more other fields in the database. The advantage of computed fields is that there is no chance of human error producing a mistake in the calculation. The result of the calculation also takes no time to do.

The SCOTTISH FOOTBALL TEAMS database displays the length and width of each club's pitch. A calculation field will be created to calculate the pitch dimensions (the length multiplied by the width). Another advantage is that if the length or the width changes then the dimensions will also automatically change immediately.

What you have to do! - Calculated Fields

How to make a Calculated Fields! Click to Go Larger Screen

1. Watch Video 8, open the database file SCOTTISH FOOTBALL TEAMS and:
2. Follow the steps shown in the video to create a new calculated field called dimensions.

Although a new field has been created, it doesn't appear on the layout of the database. To get the new field to appear, the layout has to be changed or a new one created.

3. Follow the steps shown in the second half of the video to add the new dimensions field to the layout.

Mark off Exercise 14 in your Progress Grids

What you have to do! - More Practice with Calculated Fields

Open the FOOTBALL TEAM KITS database file and where required enter your answers in the Credit Section of your your PROGRESS GRIDS.

1. Create a computed field to display the value if the stock in hand. This found by multiplying the stock level by the price of a kit.
2. Create another computed field (called stock warning) which displays a message Low Stock, but only IF the stock level is less than 10. This should be created using an IF function similar to the way you used it, in the spreadsheet topic. Make sure the calculation result box is set to text when creating the field
3. How many kits are displaying a low stock warning?

Mark off Exercise 15 in your Progress Grids

What you should be able to do now!

• Describe a CALCULATED field and explain the advantages of using calculated fields in a database.

• Set up a calculated field using the information from other database fields in the record.

• Use the IF function as part of the calculated field so that it can make a decision depending on a comparison or test used as part of the IF function.

Continue to Section 8: Using Passwords