How can I create a control that checks if an employee updated his/her own assignment record?

While the requirement is very straightforward and I can easily achieve it by writing a simple SQL, but it is proving to be a daunting task to configure the same in Advance HCM Controls. I am playing around with various objects, but unable to find out the correct way to perform the 'joins', as I am creating a model for the first time. Does anyone has any experience in this who can provide some guidance? Thank you!