Nested Sum( ) query is not working in mysql - nested

Question

i'm having a problem in calculating total bill of a ptient. I have three tables named as "test", "pharmacy", "check".
Columns in test are:
patient_ID
testname
rate
Columns in pharmacy are:
patient_ID
medicineDescription
qty
rate
Columns in check are:
patient_ID
doctorID
fees
date
I have a table Bill that will store total amount of a patient.
patient_ID
amount
date
I have used the following query. But it's giving the following error.
$result = mysqli_query($data, "SELECT patient_ID, (SUM(pharmacy.qty*pharmacy.rate ) + SUM(test.rate) + SUM(check.fees))
AS total FROM pharmacy, test, check WHERE patient_ID= '$pID'" );

Answer 1

Correct query should be, closing bracket was missing at the end of subquery (... AS total FROM pharmacy**)**):
$result = mysqli_query ($data, "SELECT patient_ID,
(SUM(pharmacy.qty*pharmacy.rate ) + SUM(test.rate) + SUM(check.fees)) AS total FROM pharmacy),
test,
check
WHERE patient_ID= '$pID'" );

Answer 2

You have three tables in your from clause, but with no join condition - this means you're pairing each row with all the other rows, which is obviously not what you intended. One way to handle this is to use proper joins:
SELECT p.patient_id, pharmacy_sum + test_sum + fees_sum AS total
FROM (SELECT patient_id, SUM(qty * rate) AS pharmacy_sum
FROM pharmacy
WHERE patient_ID= '$pID'
GROUP BY patient_id) p
JOIN (SELECT patient_id, SUM(rate) AS test_sum
FROM test
WHERE patient_ID= '$pID'
GROUP BY patient_id) t ON p.patient_id_id = t.patient_id
JOIN (SELECT patient_id, SUM(fees) AS fees_sum
FROM check
WHERE patient_ID= '$pID'
GROUP BY patient_id) c ON p.patient_id_id = c.patient_id