>I need to develop a report that lists the centers and all the patients that belong to that center along with their laboratory results. The report should pull the data from the following tables:
>
>Patients
>Centers
>Laboratory
>
>All contains a linked field: Patient_id
>
>How can I set relation to all three tables so that once finds all the patients in one center, it'll just move on to the next...
.
.

One good solution is SQL view, as Dore said, but if you insist on indexes and
relations there is one small 'bug' and workarround that is good to know about.
If you setting nested one-to-menu relationships using dataenvironment
set skip will not work properly for granchild table e.g. dataenvironment will automaticaly set 'set skip' only to first child, therefore correction
is needed to be done through code (load method);

*********************
select tableParent
set skip to FirstChild,GranChild
*********************

All the best
Sergio