mysql> SELECT * FROM items;
+---------+------------------------+--------+-------------+
| item_id | name                   | price  | category_id |
+---------+------------------------+--------+-------------+
|       1 | ローマのテーブル       | 150000 |           1 |
|       2 | げーたるーど2000 500ml |    370 |           2 |
|       3 | 原始肉                 |   2500 |           3 |
|       4 | 魅惑の椅子             | 100000 |           1 |
+---------+------------------------+--------+-------------+
4 rows in set (0.00 sec)

mysql> SELECT * FROM item_category;
+-------------+---------------+
| category_id | category_name |
+-------------+---------------+
|           1 | 家具          |
|           2 | 飲料          |
|           3 | 食品          |
+-------------+---------------+
3 rows in set (0.00 sec)

mysql> SELECT * FROM items INNER JOIN item_category USING(category_id) ORDER BY price;
+-------------+---------+------------------------+--------+---------------+
| category_id | item_id | name                   | price  | category_name |
+-------------+---------+------------------------+--------+---------------+
|           2 |       2 | げーたるーど2000 500ml |    370 | 飲料          |
|           3 |       3 | 原始肉                 |   2500 | 食品          |
|           1 |       4 | 魅惑の椅子             | 100000 | 家具          |
|           1 |       1 | ローマのテーブル       | 150000 | 家具          |
+-------------+---------+------------------------+--------+---------------+
4 rows in set (0.00 sec)

mysql> SELECT * FROM items INNER JOIN item_category USING(category_id) WHERE category_name = "家具";
+-------------+---------+------------------+--------+---------------+
| category_id | item_id | name             | price  | category_name |
+-------------+---------+------------------+--------+---------------+
|           1 |       1 | ローマのテーブル | 150000 | 家具          |
|           1 |       4 | 魅惑の椅子       | 100000 | 家具          |
+-------------+---------+------------------+--------+---------------+
2 rows in set (0.00 sec)

mysql> SELECT * FROM items INNER JOIN item_category USING(category_id) WHERE price BETWEEN 1000 AND 50000;
+-------------+---------+--------+-------+---------------+
| category_id | item_id | name   | price | category_name |
+-------------+---------+--------+-------+---------------+
|           3 |       3 | 原始肉 |  2500 | 食品          |
+-------------+---------+--------+-------+---------------+
1 row in set (0.00 sec)

mysql> SELECT COUNT(*) FROM items;
+----------+
| COUNT(*) |
+----------+
|        4 |
+----------+
1 row in set (0.00 sec)

mysql> SELECT COUNT(*) AS data_count FROM items;
+------------+
| data_count |
+------------+
|          4 |
+------------+
1 row in set (0.00 sec)