Validating data types
Keep in mind that Access supports two sets of wildcard characters: ANSI-89 and ANSI-92.Each of those standards uses a different set of wildcard characters.
However, data checking, although easy to understand and important to do, is a complex problem to solve because there are many ways data can be wrong or in a different format than we expect.Access provides a number of ways to restrict input: You can use these methods of validating data alone or in combination with each other.Data types are not optional, and provide the most basic type of data validation.The form rule is applied, and then the table rule is applied.If the table is more restrictive than the form, the rule defined for the table field takes precedence.For more information about data types, field sizes, and input masks, see the article Introduction to data types and field properties.
You can define validation rules for table fields and for controls on forms.
This article explains how to use validation rules and validation text in table fields and form controls.
A validation rule is one way to restrict input in a table field or a control (such as a text box) on a form.
By default, all .accdb and files use the ANSI-89 standard.
In the last chapter, we looked at data cleaning and the checking processes that are necessary to make that happen.
The basic approach is quite straightforward: you have fields of data and each of those fields will have expected values.