Need to help query in SQL Server - sql-server

Question

I have a question about SQL Server.
Table: patient
pn | hospid | doj
------------------------
1 | 10 | 2015-10-14
1 | 10 | 2015-05-14
1 | 10 | 2015-08-12
2nd table: patientrefs
sdate | edate | codes | descripton | pn | hospid
-------------------------------------------------------------
2015-01-01 | 2015-09-30 | 500 | active | 1 | 10
2015-01-01 | 2015-09-30 | 501 | inactive | 1 | 10
2015-10-01 | 2016-03-31 | 500 | activestill | 1 | 10
2015-10-01 | 2016-03-31 | 501 | inactive | 1 | 10
2013-03-09 | 2013-09-12 | 300 | inactive | 1 | 10
Both table common columns pn + hospid and patient tables related dos between sdate and edate of patientrefs table.
And in patientrefs table descritpton=inactive and date between condition satisfy then codes we consider inactivecodes
In patientrefs table descritpton<>inactive and date between condition satisfy then codes we consider activecodes
Based on this above table I want output like this:
pn|hospid|doj |inactivecodes| activecodes
------------------------------------------------
1 |10 |2015-05-14 | 501 | 500
1 |10 |2015-08-12 | 501 | 500
1 |10 |2015-10-14 | 501 | 500
I tried like this:
select
a.pn, a.hospid, a.doj,
case when b.descripton <> 'inactive' then b.codes end activecodes,
case when b.descripton = 'inactive' then b.codes end inactivecodes
from
patient a
left join
patientrefs b on a.pn = b.pn and a.hospid = b.hospid
and a.doj between b.sdate and b.edate
But that query is not returning the expected result.
And I tried another way
select
a.pn, a.hospid, a.doj, b.codes as inactivecodes
from
patient a
left join
patientrefs b on a.pn = b.pn and a.hospid = b.hospid
and a.doj between b.sdate and b.edate
where
b.descripton = 'inactive'
select
a.pn, a.hospid, a.doj, b.codes as activecode
from
patient a
left
patientrefs b on a.pn = b.pn and a.hospid = b.hospid
and a.doj between b.sdate and b.edate
where
b.descripton <> 'inactive'
Here the individual queries return the expected result, but I need active and inactivecodes in the above expected output format.
Please tell me how to write query to get my expected result in SQL Server

Answer 1

You can do this using conditional aggregation:
SELECT
p.pn,
p.hospid,
p.doj,
inactivecodes = MAX(CASE WHEN pr.description = 'inactive' THEN pr.codes END),
activecodes = MAX(CASE WHEN pr.description = 'active' THEN pr.codes END)
FROM patient p
LEFT JOIN patientrefs pr
ON p.pn = pr.pn
AND p.hospid = pr.hospid
AND p.doj BETWEEN pr.sdate AND pr.edate
GROUP BY
p.pn, p.hospid, p.doj