Take a look at this quick and clear explanation of how to set Validation Rules in Microsoft Access via a table.
The validation rules use the same logical expressions that can be found typically in criteria of a query and must return a logical value of either TRUE or FALSE in order to accept or reject the value and trigger an exception (validation text property). This simple property is easier to apply than attaching a macro or VBA code to an event which means learning VBA programming!
Additionally, you can set validation rules in a form too but remember this will only be available in the one form compared to a table which other forms inherit making it more globally available.
Finally, don’t confuse validation rules for field in a table which this video tutorial is about to validation rules for a record which is also available in a table.
I would love to hear from you by commenting below on how you use validation rules perhaps sharing some examples for other members to see and understand.