SQL Server - Pivot Column and Count number of Physician Instances - sql

Question

I'm having issues with my pivot statement. Essentially the problem is we have a set of patients who have been seen by different physicians during a set time period. The patients could have seen the physician multiple times during this time period. The goal is to be able to have an output where each line represents one patient and the different physicians have their own respective column where a running count for the number of encounters that a specific patient has had with the physician is present.
My query result:
Patient_ID
Age
Sex
Race
Ethnicity
Insurance
Physician
123
60
Male
White
Not Hisp
Public
Phys123
123
60
Male
White
Not Hisp
Public
Phys123
123
60
Male
White
Not Hisp
Public
Phys123
123
60
Male
White
Not Hisp
Public
Phys456
456
40
Female
Black
Not Hisp
Private
Phys456
456
40
Female
Black
Not Hisp
Private
Phys456
789
70
Female
White
Hisp
Private
Phys789
Here's example DML and DDL as a table variable to demonstrate:
DECLARE #Visits TABLE (Patient_ID INT, Age SMALLINT, Sex NVARCHAR(10), Race NVARCHAR(10), Ethnicity NVARCHAR(10), Insurance NVARCHAR(10), Physician NVARCHAR(10))
INSERT INTO #Visits (Patient_ID, Age, Sex, Race, Ethnicity, Insurance, Physician) VALUES
(123, 60, 'Male' ,'White' ,'Not Hisp' ,'Public' ,'Phys123'),
(123, 60, 'Male' ,'White' ,'Not Hisp' ,'Public' ,'Phys123'),
(123, 60, 'Male' ,'White' ,'Not Hisp' ,'Public' ,'Phys123'),
(123, 60, 'Male' ,'White' ,'Not Hisp' ,'Public' ,'Phys456'),
(456, 40, 'Female' ,'Black' ,'Not Hisp' ,'Private' ,'Phys456'),
(456, 40, 'Female' ,'Black' ,'Not Hisp' ,'Private' ,'Phys456'),
(789, 70, 'Female' ,'White' ,'Hisp' ,'Private' ,'Phys789')
Phys123 - Susan Marshal
Phys456 - Mike Andrews
Phys789 - Michelle Bell
What I expected:
Patient_ID
Age
Sex
Race
Ethnicity
Insurance
Susan Marshal
Mike Andrews
Michelle Bell
123
60
Male
White
Not Hisp
Public
3
1
0
456
40
Female
Black
Not Hisp
Private
0
2
0
789
70
Female
White
Hisp
Private
0
0
1

Answer 1

Using the example table variable from the question, you can perform a pivot after joining to a source which contains the names. In this example I've used a values construct since there was no example data for that.
SELECT p.Patient_ID, p.Age, p.Sex, p.Race, p.Ethnicity, p.Insurance, p.[Michelle Bell], p.[Mike Andrews], p.[Susan Marshal]
FROM (
SELECT v.Patient_ID, v.Age, v.Sex, v.Race, v.Ethnicity, v.Insurance, A.Physician, A.Name
FROM #Visits v
INNER JOIN (VALUES
('Phys123', 'Susan Marshal' ),
('Phys456', 'Mike Andrews'),
('Phys789', 'Michelle Bell')
)A(Physician, Name)
ON v.Physician = a.Physician
) a
PIVOT (
COUNT(a.Physician) FOR a.Name IN ([Susan Marshal],[Mike Andrews],[Michelle Bell])
) p
Patient_ID
Age
Sex
Race
Ethnicity
Insurance
Michelle Bell
Mike Andrews
Susan Marshal
123
60
Male
White
Not Hisp
Public
0
1
3
456
40
Female
Black
Not Hisp
Private
0
2
0
789
70
Female
White
Hisp
Private
1
0
0
It is worth pointing out that you must provide the values to the pivot explicitly. This can be done via dynamic SQL, but it does increase the complexity. If you have a limited number of names you need to include it's possibly better to just hard code them.