When creating a script to add a new field to a table, you should consider two actions:

Create a rollback script that removes the field. A rollback script is a script that can undo the changes made by the original script, in case something goes wrongor the changes need to be reverted. A rollback script is a good practice to have, as it can help to restore the previous state of the database and avoid any errors or inconsistencies. In this case, the rollback script should remove the new field from the table, and any other changes that were made by the original script.

Create a script that adds the field and then populate it. A script that adds the field and then populate it is a script that can create the new field in the table, and then fill it with data from another table or source. This way, you can ensure that the new field has valid and consistent data, and that it can be used by the report in the upcoming release. In this case, the script should add the new field to the customer table, and then populate it with data from another table that contains the data used in the calculation.