How can you define two database tables to minimize maintenance effort for the fields CHANGE_DATE and CHANGE_TIME?

Defining a structure that includes the fields CHANGE_DATE and CHANGE_TIME and then including this structure in both database tables is the most efficient approach. This method promotes consistency because it allows for a single definition of the structure, ensuring that any changes made to the structure automatically propagate to both tables. Consequently, the maintenance effort is significantly reduced, as there is only one place to update field definitions, and this reduces the risk of discrepancies between the two tables.

Using a structure also enhances data integrity and reduces redundancy. It facilitates better database design practices by keeping the definitions centralized, which can lead to easier understanding and management of the database schema.

The other approaches, while functionally possible, introduce more complexity and maintenance challenges. Defining an append structure might still require you to manage the data at two locations, while copying fields would necessitate manual updates and could lead to inconsistent data if one was updated without the other. Lastly, defining the fields separately in each table would lead to duplication of definitions, increasing maintenance tasks when changes are needed.