title: Is there a Validation Rule that would allow the restriction of input values to be only of those that is present in another table?
body: <p>There are 3 tables in my Access database:</p>
  <ol>
  <li>Product</li>
  </ol>
  <ul>
  <li>Primary Key: Prod_Code</li>
  </ul>
  <ol start="2">
  <li>Supplier</li>
  </ol>
  <ul>
  <li>Primary Key: Supp_Code</li>
  </ul>
  <ol start="3">
  <li>ProductSupplierPrice</li>
  </ol>
  <ul>
  <li>Foreign Keys: Prod_Code, Supp_Code</li>
  </ul>
  <p>Essentially I created the third in order to map a product's price from a particular supplier, because a product's price differs per supplier.</p>
  <p>I need to make a validation rule so that the values inputted for the foreign key attributes of the ProductSupplierPrice, are only the primary keys that already exist in Product and Supplier.</p>
  <p>Is there a function that states a rule of something like IN(SELECT Prod_Code FROM Product)?</p>