The object is linked to the record in the database table where the value in the key column matches the link value on the object. If you edit the link value, you link the object to a different record in the table.
For example, a database has a record for each piece of equipment. The link template for the database table specifies the serial number column as the key column. If you replace a piece of equipment, you must edit the link value on the object in the drawing to reflect the new serial number. This links the object to the record with the new serial number.