Access provides different data types ” field formats that define the kind of data the field can accept ”which cover a wide variety of data. When you choose a data type for a field, Access will accept data entered only in the format specified by the data type. Selecting the appropriate data type makes it easier for users to enter and retrieve information in the database tables. It also acts as a check against incorrect data being entered. For example, a field formatted to accept only numbers removes the possibility that a user will erroneously enter text into the field.
You can change the data type for a field even after you have entered data in it. However, you might need to perform a potentially lengthy process of converting or retyping the field's data when you save the table. If the data type in a field conflicts with a new data type setting, you may lose some or all of the data in the field.
Once you've selected a data type, you can begin to work with field properties. A field property is an attribute that defines the field's appearance or behavior in the database. The number of decimal places displayed in a numeric field is an example of a property that defines the field's appearance. A property that forces the user to enter data into a field rather than leave it blank controls that field's behavior. In Design view for tables, Access provides a list of field properties, called the properties list , for each data type.