How many attributes are related to the object sample no. 7 on image no. 4?
How many attributes refers to ATT_CLASS_ID; object sample no. 7 on image no. 4 refers to IMG_ID = 4 and OBJ_SAMPLE_ID = 7
SELECT COUNT(ATT_CLASS_ID) FROM IMG_OBJ_ATT WHERE IMG_ID = 4 AND OBJ_SAMPLE_ID = 7