Final answer:
A declarative solution for deleting a record when a field value changes can be implemented using a database trigger, specifically an AFTER UPDATE trigger that checks if the field value has changed and deletes the record if the condition is met.
Step-by-step explanation:
The question pertains to creating a declarative solution for the action of deleting a record when the value of a field changes within a database. In many database systems, this can be achieved by setting up a trigger. A trigger is a database object that is automatically executed or fired when certain events occur. Specifically, you can create an AFTER UPDATE trigger on the table that contains the record you want to monitor. In the body of the trigger, you would specify the condition to check if the field value has changed and include the logic to delete the record if it meets the condition. For example, in SQL:
CREATE TRIGGER DeleteRecordTrigger
AFTER UPDATE ON your_table
FOR EACH ROW
BEGIN
IF OLD.your_field <> NEW.your_field THEN
DELETE FROM your_table WHERE id = OLD.id;
END IF;
END;
Note that actual syntax and capabilities can vary depending on the database management system (DBMS) you are using. It is essential to ensure that such a trigger does not create unwanted side effects or performance issues within your application.