This query delivers a list of discharged patients with rendering provider and discharge date. If the patient was seen by more than one provider, he or she will appear multiple times in the list:

SELECT DISTINCT pt.lastname, pt.firstname, pt.id, pr.provcode, pt.dischargedate
FROM providers pr
JOIN jcharges jc ON jc.providernum = pr.providernum
JOIN patients pt ON jc.ptnum = pt.ptnum
WHERE pt.dischargedate IS NOT NULL
ORDER BY pt.lastname, pt.firstname, pt.id, pr.provcode

To sort by provider, rather than patient name, just change the ORDER BY clause:

SELECT DISTINCT pt.lastname, pt.firstname, pt.id, pr.provcode, pt.dischargedate
FROM providers pr
JOIN jcharges jc ON jc.providernum = pr.providernum
JOIN patients pt ON jc.ptnum = pt.ptnum
WHERE pt.dischargedate IS NOT NULL
ORDER BY pr.provcode, pt.lastname, pt.firstname, pt.id