CREATE TABLE trust (source_u_id NUMBER, target_u_id NUMBER, trust NUMBER)
CREATE TABLE useracct (u_id NUMBER, name CLOB)
CREATE TABLE review (a_id NUMBER, u_id NUMBER, i_id NUMBER, rating NUMBER, rank NUMBER)
CREATE TABLE item (i_id NUMBER, title CLOB)

Find the number of items without any review.
SELECT COUNT(*) FROM item WHERE NOT i_id IN (SELECT i_id FROM review)
SELECT COUNT(*) FROM "item" WHERE NOT "i_id" IN (SELECT "i_id" FROM "review")