SQL display data according to criteria - sql

Question

A) I have a table of doctors. Each doctor has a unique username, as well as a rating and a specialty. There is a also a table of Surgeries. It contains (among other things)
an attribute with doctor's unique username. It is not unique.
I'm trying to create a table that displays for each specialty. the data:
Speciality | Avg. Rating for Each Speciality | # of surgeries performed by Speciality
(first column is just the name of the specialty)
My best so far:
SELECT D.Speciality,t1.Avg, t0.CPT FROM DOCTOR as D
INNER JOIN(
SELECT AVG(AvgRating) as Avg, Speciality
FROM Doctors as D1
GROUP BY D1.Speciality
) as t1 ON D.Speciality=t1.Speciality
INNER JOIN(
SELECT COUNT(CPT) as CPT, Speciality
FROM PERFORM_SURGERY AS P
GROUP BY P.Speciality
)t0 ON t0.SPECIALITY=D.SPECIALITY
;
B) The doctor table includes a unique username and a non-unique name. There is also a Prescription table. It contains the both the doctor's username and patient's username.
Now there are 3 more tables that we need. One is a Req_surgery, Surgery and Visit.
Req_surgery contains the Doctor's username and a CPT (CPT is unique). The Surgery table has a primary key of CPT, and it also contains the cost of the surgery. Visit contains the doctor's username and patient's username as well as the cost of the visit.
I want a table with:
Doctor Name | No of Patients Seen | No of Prescriptions written | Total Billing
that lists each Doctor's name and the required info.
So far I have:
SELECT t1.name, t3.Visits, t2.Prescriptions, t4.money
FROM DOCTOR as D
INNER JOIN(
SELECT (FName + LName) as name, Username
FROM DOCTOR
) t1 ON t1.userName=D.username
INNER JOIN(
SELECT DUsername, COUNT(DateVisit) AS Prescriptions
FROM PRESCRIPTION
WHERE MONTH(DateVisit) = $month
AND YEAR(DateVisit)=$year
)t2 ON D.Username = t2.DUsername
INNER JOIN(
SELECT COUNT(DATEVISIT) as Visits, DUsername
FROM VISIT as V
WHERE MONTH(DateVisit) = $month
AND YEAR(DateVisit)=$year
)t3 ON D.Username=t3=DUsername
I didn't even finish because (a) I know what I have is wrong and I don't know how to fix it, and (b) I don't see how to compute the revenue for each doctor.
Doctor has primary key of Username.
Surgeries has primary key of CPT.
Req_Surgery has foreign key of the Doctor's Username (henceforth DU) that references Doctor(Username).

Answer 1

SELECT (FName + LName) as name, t3.Visits, t2.Prescriptions, t4.money
FROM DOCTOR as D
INNER JOIN(
SELECT DUsername, COUNT(DateVisit) AS Prescriptions
FROM PRESCRIPTION
WHERE MONTH(DateVisit) = $month
AND YEAR(DateVisit)=$year
GROUP BY DUsername
)t2 ON D.Username = t2.DUsername
INNER JOIN(
SELECT COUNT(DATEVISIT) as Visits, DUsername
FROM VISIT as V
WHERE MONTH(DateVisit) = $month
AND YEAR(DateVisit)=$year
GROUP BY DUsername
)t3 ON D.Username=t3.DUsername
I added grouping by DUsername to get the numbers for each doctor. Also I removed the t1 because in fact it's the same as D