How to limit creation of related entries


I have a Pets table, that has a number of pets and a Training Journal table that tracks a number of items that need to be done on a daily basis. However, I want to make this so that you can only add one journal entry per day. Any idea how I would go about doing this?

It sounds that Training Journal table is child table of Pets table.

if so , one approach is to have a date column in the Training Journal table with a valid_if expression that does not allow duplicate entries for dates for that pet from the parent table.

The last section in the help article below describes the valid_if to disallow duplicates.