Question

hey guys, just having a bit of difficulty with a query, i’m trying to figure out how to show the most popular naturopath that has been visited in a centre. My tables look as follows;

Patient(patientId, name, gender, DoB, address, state,postcode, homePhone, businessPhone, maritalStatus, occupation, duration,unit, race, registrationDate , GPNo, NaturopathNo)

and

Naturopath (NaturopathNo, name, contactNo, officeStartTime, officeEndTime, emailAddress)

now to query this i’ve come up with

SELECT count(*), naturopathno FROM dbf10.patient WHERE naturopathno != 'NULL' GROUP BY naturopathno;

which results in;

  COUNT(*) NATUROPATH
     2 NP5
     1 NP6
     3 NP2
     1 NP1
     2 NP3
     1 NP7
     2 NP8

My question is, how would I go about selecting the highest count from this list, and printing that value with the naturopaths name? Any suggestions are very welcome,

Answer 1

You can use the RANK analytic function – this will assign rank “1” to the topmost naturopath, or naturopaths if there is a tie for first place:

SELECT (select name from Naturopath n
        where n.NaturopathNo = q.naturopathno)
       as TopNaturopathName,
      ,q.patients
FROM (
 SELECT naturopathno, patients,
        RANK() OVER (ORDER BY patients DESC) rnk
 FROM (
  SELECT COUNT(*) AS patients, naturopathno
  FROM dbf10.patient
  WHERE naturopathno is not null
  GROUP BY naturopathno
 )
) q
WHERE rnk = 1;