How many object samples in image no.1 are in the class of "man"?
object samples refers to OBJ_CLASS_ID; image no.1 refers to IMG_ID = 1; in the class of "man" refers to OBJ_CLASS = 'man'
SELECT SUM(CASE WHEN T1.OBJ_CLASS = 'man' THEN 1 ELSE 0 END) FROM OBJ_CLASSES AS T1 INNER JOIN IMG_OBJ AS T2 ON T1.OBJ_CLASS_ID = T2.OBJ_CLASS_ID WHERE T2.IMG_ID = 1