Trying to combine multiples of a key ID into single row, but with different values in columns - sql

Question

TSQL - SQL Sever
I'm building a report to very specific requirements. I'm trying to combine multiples of a key ID into single rows, but there's different values in some of the columns, so GROUP BY won't work.
SELECT count(tt.Person_ID) as CandCount, tt.Person_ID,
CASE e.EthnicSuperCategoryID WHEN CandCount > 1 THEN 10 ELSE e.EthnicSuperCategoryID END as EthnicSuperCategoryID,
CASE e.Ethnicity_Id WHEN 1 THEN 1 ELSE 0 END as Black ,
CASE e.Ethnicity_Id WHEN 2 THEN 1 ELSE 0 END as White ,
CASE e.Ethnicity_Id WHEN 3 THEN 1 ELSE 0 END as Asian,
etc
FROM T_1 TT
JOINS
WHERE
GROUP
Msg 102, Level 15, State 1, Line 4
Incorrect syntax near '>'.
Here's the results (without the first CASE). Note person 3 stated multiple ethnicities.
SELECT count(tt.Person_ID) as CandCount, tt.Person_ID,
CASE e.Ethnicity_Id WHEN 1 THEN 1 ELSE 0 END as Black ,
CASE e.Ethnicity_Id WHEN 2 THEN 1 ELSE 0 END as White ,
CASE e.Ethnicity_Id WHEN 3 THEN 1 ELSE 0 END as Asian,
etc
FROM T_1 TT
JOINS
WHERE
GROUP
That’s expected, but the goal would be to assign multiple ethnicities to Ethnicity_Id of 10 (multiple). I also want them grouped on a single line.
So the end result would look like this:
So my issue is two fold. If the candidate has more than 2 ethnicities, assign the records to Ethnicity_Id of 10. I also need duplicated person IDs grouped into a single row, while displaying all of the results of the columns.

Answer 1

This should bring your desired result:
SELECT Person_ID
, ISNULL(ID_Dummy,Ethnicity_ID) Ethnicity_ID
, MAX(Black) Black
, MAX(White) White
, MAX(Asian) Asian
FROM #T T
OUTER APPLY(SELECT MAX(10) FROM #T T2
WHERE T2.Person_ID = T.Person_ID
AND T2.Ethnicity_ID <> T.Ethnicity_ID
)EthnicityOverride(ID_Dummy)
GROUP BY Person_ID, ISNULL(ID_Dummy,Ethnicity_ID)

Answer 2

You want conditional aggregation. Your query is incomplete, but the idea is:
select
person_id,
sum(case ethnicity_id = 1 then 1 else 0 end) as black,
sum(case ethnicity_id = 2 then 1 else 0 end) as white,
sum(case ethnicity_id = 3 then 1 else 0 end) as asian
from ...
where ...
group by person_id
You might want max() instead of sum(). Also I did not get the logic for column the second column in the desired results - maybe that's just count(*).

Answer 3

This would be my approach
SELECT
person_id,
CASE WHEN flag = 1 THEN Ethnicity_Id ELSE 10 END AS Ethnicity_Id,
[1] as black,
[2] as white,
[3] as asian
FROM
(
SELECT
person_id,
Ethnicity_Id as columns,
1 as n,
MAX(Ethnicity_Id) over(PARTITION BY person_id) as Ethnicity_Id,
COUNT(Ethnicity_Id) over(PARTITION BY person_id) as flag
FROM
#example
) AS SourceTable
PIVOT
(
MAX(n) FOR columns IN ([1], [2], [3])
) AS PivotTable;
Pivot the Ethnicity_Id column into multiples columns, Using constant
1 to make it complain with your expected result.
Using Max(Ethnicity_Id) with Partition By to get the original
Ethnicity_Id
Using Count(Ethnicity_Id) to flag if a need to raplace Ethnicity_Id
with 10 bc there is more that 1 row for that person_id
If you need to add more Ethnicitys add the ids in ... IN ([1], [2], [3]) ... and in the select