Every table in Access is made up of fields. The properties of a field describe the characteristics and behavior of data added to that field. A field's data type is the most important property because it determines what kind of data the field can store. This article describes the data types and other field properties available in Access, and includes additional information in a detailed data type reference section.
Overview
Data types can seem confusing for example, if a field's data type is Text, it can store data that consists of either text or numerical characters. But a field whose data type is Number can store only numerical data. So, you have to know what properties are used with each data type.
A field's data type determines many other important field qualities, such as the following:
Which formats can be used with the field.
The maximum size of a field value.
How the field can be used in expressions.
Whether the field can be indexed.
A field's data type can be predefined or you will select a data type depending on how you create the new field. For example, if you create a field from the Datasheet view and:
Use an existing field from another table, the data type is already defined in the template or in the other table.
Enter data in a blank column (or field), Access assigns a data type to the field based on the values that you enter or you can assign the data type and format for the field.
On the Modify Fields tab, in the Fields & Columns group, click Add Fields, Access displays a list of data types that you can select from.