Click above to get retro games delivered to your door ever month!

   Indicates the criterion for the quick positioning of the child file on the
   first record that satisfies the 1:N relation.

   The value of this parameter can be an expression applied to the fields, a
   user defined function or a memory variable. When modifying, the Alt-1
   keys will help you rapidly set the desired expression. The user functions
   can be defined in both the Symbols environment and within this
   context.

   Modifying the primary key directly in the relations environment, although
   accepted, is not the usual way of working.
    Whenever the primary positioning key should be modified, it is better to
   apply the changes using the Link button on the definition frame
   (Space).