UPDATE t
SET t.Member1=r.Member1,
t.Member2= r.Member2,
t.Member3= r.Member3,
t.Member4= r.Member4,
t.Member5= r.Member5
FROM YourTable t
INNER JOIN
(
SELECT t1.IDcol,
MAX(CASE WHEN f.ID=1 THEN f.Val ELSE NULL END) AS Member1,
MAX(CASE WHEN f.ID=2 THEN f.Val ELSE NULL END) AS Member2,
MAX(CASE WHEN f.ID=3 THEN f.Val ELSE NULL END) AS Member3,
MAX(CASE WHEN f.ID=4 THEN f.Val ELSE NULL END) AS Member4,
MAX(CASE WHEN f.ID=5 THEN f.Val ELSE NULL END) AS Member5
FROM YourTable t1
CROSS APPLY dbo.ParseValues(t.usernamecol,',')f
GROUP BY t1.IDcol
)r
ON r.IDCol=t.IDCol