Need to sub count in a count - sql

Question

In the following, we get a count of how many times a patient did not show for an medical appointment (NOSHOW). It is based on if they did not show for the current day, then we display their count of this from the past. How can I get also the department that they did not show for? We have 6 different medical department so the manager wants to see if the problem is only for say dental, or for all. This will assist them from perhaps not booking someone etc.
SELECT Distinct
Appt_DateTime j,
Patient_Name j,
Appt_Status j,
Appt_Sched_Department_ID j,
Appt_Sched_Department_Descr j,
Patient_id j,
Patient_number j,
Appt_NoShow_Date j,
ISNULL(P.NotShowCount,0) AS NotShowCount
FROM
vwGenPatInfo vwGenPatInfo j
INNER JOIN vwGenPatApptInfo vwGenPatApptInfo ON vwGenPatInfo.Patient_ID=vwGenPatApptInfo.Patient_ID
LEFT JOIN (
SELECT Patient_ID, COUNT(Appt_Status) AS NotShowCount
FROM (SELECT Appt_DateTime, Appt_Status, Appt_Sched_Department_ID, Appt_Sched_Department_Descr, Appt_NoShow_Date, Patient_ID
FROM vwGenPatapptInfo AS vwGenPatApptInfo
WHERE (Appt_Status = 'N') AND (Appt_DateTime < DATEADD(day, DATEDIFF(day, 0, GETDATE()), - 1))) AS L
GROUP BY
Patient_ID) AS P ON vwGenPatInfo.Patient_ID=P.Patient_ID
WHERE
vwGenPatApptInfo.Appt_Status='N'
ORDER BY
vwGenPatApptInfo.Appt_Sched_Department_ID,
vwGenPatApptInfo.Appt_DateTime
the data currently is like this: the last number is the count of previous noshows. So we want to break this down like Adult Medicine_NS 3, Dental_NS 9. the datetime showing is the noshow from previous day. The call room will call them to re-schedule.
Patient_Name Appt_Sched_Departmen Appt_NoShow_Date Previous No Show Count
8/31/2016 No Shows 8/30/2016
Patient_number
Sinca Blay Adult Medicine 8/30/2016 12:05:46PM 12
Wiske Semns Adult Medicine 8/30/2016 5:25:32PM 4
Rose Alhar Adult Medicine 8/30/2016 5:57:01PM 6

Answer 1

You could use analytic, aggregate and ranking window functions for this.
Here is an untested query to give you an idea:
SELECT Patient_ID,
Patient_Name,
Appt_Sched_Department_ID,
Appt_Sched_Department_Descr,
Appt_NoShow_Date_Today,
Appt_NoShow_Date_Prev,
NotShowCount
FROM (SELECT app.Patient_ID,
pat.Patient_Name,
app.Appt_Sched_Department_ID,
app.Appt_Sched_Department_Descr,
app.Appt_DateTime AS Appt_NoShow_Date_Today,
LEAD(app.Appt_DateTime)
OVER (PARTITION BY app.Patient_ID
ORDER BY app.Appt_DateTime DESC) AS Appt_NoShow_Date_Prev,
COUNT(app.Appt_Status)
OVER (PARTITION BY app.Patient_ID) AS NotShowCount,
ROW_NUMBER()
OVER (PARTITION BY app.Patient_ID
ORDER BY app.Appt_DateTime DESC) AS rn
FROM vwGenPatApptInfo app
INNER JOIN vwGenPatInfo pat
ON pat.Patient_ID = app.Patient_ID
WHERE app.Appt_Status = 'N'
) AS base
WHERE rn = 1
AND Appt_NoShow_Date_Today >= DATEADD(day, DATEDIFF(day, 0, GETDATE()), 0)
ORDER BY Appt_Sched_Department_ID,
Appt_NoShow_Date_Today
The inner query gets all records with status 'N', but adds information:
Appt_NoShow_Date_Prev: the Appt_DateTime value of the next record if the records are sorted by descending Appt_DateTime (for the same patient: this is the "window").
NotShowCount: The number of records in that window.
rn: the sequential record number in that window, again when records are sorted by descending Appt_DateTime.
The outer query only keeps the records with rn = 1, which means: the record with the most recent Appt_DateTime per patient. As a second condition, this Appt_DateTime must be today (after last midnight): this makes sure we only list patients which were absent today.