Potrebbe essere necessario utilizzare una tabella temporanea o una variabile di tabella come mostrato di seguito
DECLARE @t TABLE (
ID INT
,SuppressionTypeID INT
,PersonID INT
)
INSERT INTO @t
SELECT 1
,1
,123
UNION ALL
SELECT 2
,1
,456
UNION ALL
SELECT 3
,2
,456
DECLARE @t1 TABLE (
ID INT
,SuppressionTypeID INT
,PersonID INT
,firstid INT
)
INSERT INTO @t1
SELECT *
,NULL
FROM @t
UPDATE t1
SET t1.firstid = t2.firstid
FROM @t1 AS t1
INNER JOIN (
SELECT personid
,min(SuppressionTypeID) AS firstid
FROM @t1
GROUP BY personid
) AS t2 ON t1.PersonID = t2.PersonID
SELECT coalesce(t2.firstid, t1.SuppressionTypeID) AS SuppressionTypeID
,count(DISTINCT t2.personid) AS count
FROM @t1 AS t1
LEFT JOIN @t1 AS t2 ON t1.personid = t2.personid
AND t1.SuppressionTypeID = t2.firstid
GROUP BY coalesce(t2.firstid, t1.SuppressionTypeID)
Il risultato è
SuppressionTypeID count
----------------- -----------
1 2
2 0
