| Lesson 3 | Data types |
| Objective | Describe the field data types available in Access. |
Access Data types
OK, so you have learned how to create a table and how to display the Table Design view--now you can use the table Design view to refine field definitions. Why, you ask, might you want to do that? The Table Design view enables you to change a field’s data type and to refine the formatting.Let’s talk a little more about data types. Access selects a data type for you when you enter the first piece of data for a field in Datasheet view. Usually, this is the correct data type.
Using the correct data type for a field is the first step toward preventing incorrect input. For instance, if you set a field’s data type to number, Access displays an error if the user tries to enter anything but a number. There are other methods for controlling data entry, and we’ll explore some of these as we go, but this is the simplest. The following table tells you about each data type:
Data Type | Allowed Data |
|---|---|
| Text | Letters, numbers, punctuation, spaces, and special characters. A text field holds up to 255 characters. |
| Memo | Like a text field, but longer—up to 65,535 characters. |
| Number | Numbers only--decimal points are allowed, but no other non-numerical characters. |
| Date/Time | Dates and times in a variety of standard formats. |
| Currency | Numbers with a currency sign in front of them. Access will add the currency sign when the data type is Currency. |
| AutoNumber | A number assigned by Access. Starts at 1 for the first record, and increments upward. Primary key fields created by Access are always AutoNumber fields. |
| Yes/No | One of two defined responses: it can be Yes or No, or user defined choices such as True/False, On/Off, Male/Female. Yes/No data types appear as a checkbox in each record. Toggle the value by clicking the check box or pressing the spacebar when the field is selected. |
| OLE Object | A picture, sound, or some other object contained in an electronic file. |
| Hyperlink | Hyperlink addresses such as e-mail addresses and URLs (Web site addresses). |
| Lookup Wizard | This is not technically a data type, but it runs a wizard that allows you to create a drop-down list so that the user can choose from a list of possibilities. This is often used to choose a value from another field in another table. |