Pure Transact SQL (não usando chamada SQL dinâmica que não faz parte do TSQL):
SELECT
CASE WHEN c1 IS NULL THEN 0 ELSE 1 END
+ CASE WHEN c2 IS NULL THEN 0 ELSE 1 END
+ CASE WHEN c3 IS NULL THEN 0 ELSE 1 END
+ CASE WHEN c4 IS NULL THEN 0 ELSE 1 END
+ CASE WHEN c5 IS NULL THEN 0 ELSE 1 END
+ CASE WHEN c6 IS NULL THEN 0 ELSE 1 END
+ CASE WHEN c7 IS NULL THEN 0 ELSE 1 END
+ CASE WHEN c8 IS NULL THEN 0 ELSE 1 END
FROM T