In Access entering data into tables offers many options. Learn all about adding and editing Access database entries in this free lesson.
Data validation is an important database concept. It is the process by which Access tests the data that is being entered into the database to make sure it is in an acceptable—or valid—format.
Let's say one of your database users has entered an order date of January 4, 2008, in the month/date/year format as 01/04/2008. Another user has entered an order placed on that same date in the day/month/year format as 04/01/2008. If the database is tracking all sales for the month of January 2008, it may not show both orders as placed in January, even though both were placed on the same date.
Access 2007 allows you to set field properties and data validation rules to force the person entering data to follow a specific format.
Data validation begins when data types are set during the process of building tables and fields. For example, if a field data type had been set to Currency and a text value is entered in that table field during data entry, Access will not accept an invalid format and will display a validation error, like the one below.
Data Validation Error Message
Data validation is accomplished by setting data validation rules and other field properties for various fields.
Use Expression Builder to Enter Validation Rule
Validation Rule for Category Field
Validation rules work most easily with numerical fields. Rules for text fields require you to enclose each acceptable value inside its own quotation marks, separating them with Or, as seen above.
Validation text is a specialized error message you can set to have Access tell the user entering data the specific way you want that person to enter it.
To set the validation text, enter the error message exactly as you want it to appear to users in the row directly beneath the Validation Rule row in the Field Properties section of Design view. For the validation rule we set for Category, you'd set the validation text like this:
Validation Text for Category Field
The image below shows the resulting error message users would see when the Category validation rule has been broken.
Error Message Showing Validation Text
Another way to ensure data integrity is by setting field properties such as Field Size, Format, and Required.
These are just some ways Access helps you ensure data being entered into your database is valid.