--問5
select * from items inner join item_category using(category_id) where category_name = '家具';

--問6
select * from items inner join item_category using(category_id) where price between 1000 and 50000;

--問7
select count(*) as data_count from items;

--問8
select * from items inner join item_category using(category_id) where  price = (select max(price) from items);

--問9
select * from items inner join item_category using(category_id) where name like '%の%';