I am designing a system which is based on a schema, but i don't know how to link reference tables to validate if the user has entered valid data or complete rubbish.<br><br>E.g <br>tbl_order<br>Order_id (PK)<br>Advice_no<br>Supplier_id<br>Dept_no<br>Destination_no<br>No_of_singles<br>Unique_ref_no<br><br>Reference table<br>tbl_Supplier<br>Supplier_id (PK)<br>Supplier_desc<br><br>How do i validate wether the user has entered a valid supplier number?<br><br>Can anyone help?<br>