defineRelationship and sorting

[ubay25]

I have this line on my code:
$tbl->defineRelationship("uid", "user_details", "id", "name");

The above returns the names of the users from the associated "user_details" table.
It works as expected but if I sort this field by clicking table header, it doesnt sort by "name" but by the "id".

How can I sort by "name"?