Among the patients whose C-reactive protein level is abnormal, how many of them aren't 18 yet?
C-reactive protein level is abnormal refers to CRP NOT IN('+-', '-') AND CRP > = 1.0; aren't 18 refers = CRP > = 1.0 AND SUBTRACT((YEAR(CURDATE()), YEAR(Birthday))) < 18; Should compute the number of distinct ones.
SELECT COUNT(DISTINCT T1.ID) FROM Patient AS T1 INNER JOIN Laboratory AS T2 ON T1.ID = T2.ID WHERE (T2.CRP != '-' AND T2.CRP != '+-') AND T2.CRP >= 1.0 AND STRFTIME('%Y', Date('now')) - STRFTIME('%Y', T1.Birthday) < '18'