SQL, joining two tables and selecting their max - sql

Question

I have two tables
customers_bought:
PID SID QUANTITY
---------- ---------- ----------
3289 11 12
74591 11 10
74591 12 1
74591 23 1
74591 31 1
88331 13 21
88331 31 48
customers:
PID NAME
---------- --------------------
3289 George
88331 Alice
74591 Jane
10234 Able
What I need to be able to do is list the customers who bought the greatest number of sandwiches of a single type. I also need to display the customer name, pid, sid, and quantity. This being SQL, of course it's more complicated than it sounds. I'm unsure how to join the two results I have below, here's what I have managed to do:
Code:
Select C.pid, C.name, CB.sid, CB.quantity
From customers C
Inner Join customers_bought CB
On CB.PID = C.PID;
Result:
PID NAME SID QUANTITY
---------- -------------------- ---------- ----------
3289 George 11 12
74591 Jane 11 10
74591 Jane 12 1
74591 Jane 23 1
74591 Jane 31 1
88331 Alice 13 21
88331 Alice 31 48
Code:
Select CB.sid, MAX(CB.Quantity)
From customers_bought CB
Group By CB.sid
Result:
SID MAX(CB.QUANTITY)
---------- ---------------------------------------
11 12
13 21
31 48
23 1
12 1

Answer 1

Try this one
Select
C.pid, C.name, CB.sid, ms.MaxQuentity
From customers C
Inner Join customers_bought CB
On CB.PID = C.PID
INNER JOIN
(
Select
CB.sid,
MAX(CB.Quantity) AS MaxQuentity
From customers_bought CB
Group By CB.sid
) ms ON ms.sid = CB.sid AND ms.MaxQuentity = CB.QUANTITY
You can find the Sample code in Fiddle