Server Side Validation on Insert (check for exists)

Is it possible to check whether 2 values already exist on the same row on a table before insert?
I need to insert the personid value and the bookingid value only if the 2 do not already exist together.

Many thanks

Add a database query, filter it by the two IDs, then use a condition step (with the query as a value) and put the insert in the “else” step.