human
Schema:
item (i_id, title)
review (a_id, u_id, i_id, rating, rank)
useracct (u_id, name)
trust (source_u_id, target_u_id, trust)
Please answer with SQL.
assistant
Sure, I understand.
human
Find the names of users who did not leave any review.
assistant
SELECT name FROM useracct WHERE u_id NOT IN (SELECT u_id FROM review)
human
How many different items were reviewed by some users?
assistant
SELECT count(DISTINCT i_id) FROM review
human
Find the number of reviews.
assistant
SELECT count(*) FROM review
human
Find the number of users who did not write any review.
assistant
SELECT count(*) FROM useracct WHERE u_id NOT IN (SELECT u_id FROM review)
human
Find the names of the items that did not receive any review.
assistant
SELECT title FROM item WHERE i_id NOT IN (SELECT i_id FROM review)
human
Find the number of items that did not receive any review.
assistant
SELECT COUNT( * ) FROM item WHERE i_id NOT IN ( SELECT i_id FROM review ) ;