SQL one to many on one row - sql

Question

I have a table that records the diagnosis of patient for each attendance. Patients can have more than one diagnosis.
I want one row per attendance with all diagnosis (up to 12 diagnosis). The below brings back more than one row.
select
dg.AttendanceID
, dg.PatientNumber
, dg.DiagnosisDate
, dg.Diagnosis
from
Diagnosis dg
AttendanceID PatientNumber DiagnosisDate Diagnosis
10001 123456 01-Oct-13 A
10001 123456 01-Oct-13 B
10002 123456 20-Oct-13 D
It results should look like this:
AttendanceID PatientNumber DiagnosisDate Diagnosis 1 Diagnosis 2 Diagnosis 3
10001 123456 01-Oct-13 A B
10002 123456 20-Oct-13 D
Can someone please help?

Answer 1

You can get the result by implementing the PIVOT function, but I would also suggest using the windowing function row_number() to generate the number of diagnosis for each attendanceid and patientnumber:
select attendanceid, patientnumber,
diagnosisdate,
Diagnosis1, Diagnosis2, Diagnosis3
from
(
select attendanceid, patientnumber,
diagnosisdate, diagnosis,
'diagnosis'+
cast(row_number() over(partition by attendanceid, patientnumber
order by diagnosis) as varchar(2)) seq
from diagnosis
) d
pivot
(
max(diagnosis)
for seq in (Diagnosis1, Diagnosis2, Diagnosis3)
) piv;
See SQL Fiddle with Demo. Since you know you will have up to 12 diagnosis per patient/attendance you can easily hard code the query to add the additional columns.
But if you needed a dynamic version of the code, then you could use something similar to the following:
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols = STUFF((SELECT distinct ',' + QUOTENAME(seq)
from
(
select 'diagnosis'+
cast(row_number() over(partition by attendanceid, patientnumber
order by diagnosis) as varchar(2)) seq
from diagnosis
) d
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = 'SELECT attendanceid, patientnumber,
diagnosisdate,' + #cols + '
from
(
select attendanceid, patientnumber,
diagnosisdate, diagnosis,
''diagnosis''+
cast(row_number() over(partition by attendanceid, patientnumber
order by diagnosis) as varchar(2)) seq
from diagnosis
) x
pivot
(
max(diagnosis)
for seq in (' + #cols + ')
) p '
execute sp_executesql #query;
See SQL Fiddle with Demo
Both versions give a result:
| ATTENDANCEID | PATIENTNUMBER | DIAGNOSISDATE | DIAGNOSIS1 | DIAGNOSIS2 | DIAGNOSIS3 |
|--------------|---------------|--------------------------------|------------|------------|------------|
| 10001 | 123456 | October, 01 2013 00:00:00+0000 | A | B | (null) |
| 10002 | 123456 | October, 20 2013 00:00:00+0000 | D | (null) | (null) |

Answer 2

I am not 100% sure but it should be something along those lines.
;with cte as(
select
dg.AttendanceID
, dg.PatientNumber
, dg.DiagnosisDate
, dg.Diagnosis
,ROW_NUMBER() over (partition by dg.attendanceID order by attendanceID) as seq1
,ROW_NUMBER() over (partition by dg.attendanceID, patient_no order by diagnosis) as seq2
from
Diagnosis dg
)
select
t1.attendanceID
,t1.patientNumber
,t1.diagnosisDate
,(select Diagnosis from cte t2 where t1.attendanceID=t2.attendanceID and t1.patientNumber=t2.patientNumber and t2.seq2='1') as diag1
,(select Diagnosis from cte t2 where t1.attendanceID=t2.attendanceID and t1.patientNumber=t2.patientNumber and t2.seq2='2') as diag2
,(select Diagnosis from cte t2 where t1.attendanceID=t2.attendanceID and t1.patientNumber=t2.patientNumber and t2.seq2='3') as diag3
,(select Diagnosis from cte t2 where t1.attendanceID=t2.attendanceID and t1.patientNumber=t2.patientNumber and t2.seq2='4') as diag4
,(select Diagnosis from cte t2 where t1.attendanceID=t2.attendanceID and t1.patientNumber=t2.patientNumber and t2.seq2='5') as diag5
from cte t1
where seq1= 1

Answer 3

Below is a probable solution by using cursors i am not sure if you can show it as columns as it is variable for every patient but this will show diagnosis as comma separated in one single column
DECLARE #combinedString VARCHAR(MAX),
#id int,
#Diagnosis VARCHAR(MAX)
Declare #CONCATRESULT TABLE (AttendanceID int, Question VARCHAR(MAX) )
Declare Dia cursor for
SELECT AttendanceID FROM Diagnosis
open Dia
Fetch next from Dia into #id
while ##FETCH_STATUS=0
begin
SELECT #combinedString = COALESCE(#combinedString + ', ', '') + Diagnosis,
#id=AttendanceID FROM [Prod_PostData].[dbo].[KMSFPostDataDenorm] d
WHERE AttendanceID = #id
insert into #CONCATRESULT values ( #id ,#combinedString )
SET #combinedString = null
Fetch next from Dia into #id
end
close Dia
deallocate Dia
select
dg.AttendanceID
, dg.PatientNumber
, dg.DiagnosisDate
, dg.Diagnosis
from
Diagnosis dg join (select * from #CONCATRESULT) Y on dg.AttendanceID=Y.AttendanceID