You can also apply filter on query to contain only active contracts for "prodct on contract" and then just create a simple one-many relationship. If it is not possible, could you post any sample data of those two tables and expected output?
Just to clarify, what do you exactly mean? Information whether the contract is active or is only on "contract"-table. Do you mean I should merge this information to "product on contract"-table and then filter out the lines with inactive contract information?