In the previous chapter, we looked at how we can set the required field and auto number field properties on custom fields to help improve the quality and maintain the data integrity of records in the system.
Salesforce also provides other data validation mechanisms such as:
Data validation rules can be applied to both custom and standard fields and are used to verify that the data entered in a record meets the criteria you have specified before the record can be saved.
Validation rules contain a formula or expression that evaluates the data in one or more fields and returns a value of either true or false.
The logic that is used for validation rules is to seek an error condition, ...