SELECT count(*) FROM item WHERE i_id NOT IN (SELECT i_id FROM review)
Find the number of items without any review.
[Schema (values) (types)]: | epinions_1 |  item : i_id (text) , title (number) | review : a_id (text) , u_id (number) , i_id (text) , rating (number) , rank (number) | useracct : u_id (text) , name (number) | trust : source_u_id (text) , target_u_id (number) , trust (text);