How many samples of "wall" are there in image no.2353079?
samples of "wall" refers to OBJ_SAMPLE_ID and OBJ_CLASS = 'wall' ; image no.2353079 refers to IMG_ID = 2353079
SELECT SUM(CASE WHEN T1.OBJ_CLASS = 'wall' 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 = 2353079