$($c$)$ Consider the following database schema:

DOCTOR $($doc no$,$ doctor$\_$name, specialty$)$

PATIENT $($pat id$,$ pat name, address, phone, dob$)$

VISIT $($ doc no$,$ pat id$,$ type, date, diagnosis, charge$)$

The database is kept by a medical group which consists of several physicians.

Each physician has only one specialty. Patient records are shared among the

doctors. For each patient visit, information is stored about the type $($regular

office, hospital, after hours, house call, etc.$),$ a single diagnosis for that visit, and

the charge. The visit is identified by doc$\_$no$,$ pat$\_$id and date, because a patient

may visit more than one doctor on a particular day. We assume, however, that a

patient never visits the same doctor more than once in a day.

Formulate relational algebra commands for the following queries:

Get a list of all the different specialties the physicians have.

$(2$ marks$)$

$($ii$)$ Find the names of all the doctors whose specialty is Pediatrics.

$(3$ marks$)$

$($iii$)$ Find the doc$\_$no of all doctors who saw patient Mary Adams.

$(4$ marks$)$

$($iv$)$ Get a list of the patient ids, names and addresses of all patients who

visited Dr$.$ Hubert Jones on January $15,1990.$

$(7$ marks$)$