--Q1
SELECT items.item_id AS '商品ID',
       items.name AS '商品名',
       items.price AS '価格',
       item_category.name AS 'カテゴリ名'
FROM items INNER JOIN item_category ON items.category_id = item_category.category_id
ORDER BY items.item_id ASC;

--Q2
SELECT orders.order_id AS '注文ID',
       orders.order_time AS '注文日時',
       users.name AS 'ユーザ名',
       items.name AS '商品名',
       items.price AS '価格',
       order_items.quantity AS '数量'
FROM orders
    INNER JOIN order_items ON orders.order_id = order_items.order_id
    INNER JOIN users ON orders.user_id = users.user_id
    INNER JOIN items ON order_items.item_id = items.item_id
ORDER BY orders.order_id ASC;

--Q3
SELECT orders.order_id AS '注文ID',
       orders.order_time AS '注文日時',
       users.name AS 'ユーザ名',
       SUM(items.price*order_items.quantity) AS '合計額'
FROM orders
    INNER JOIN order_items ON orders.order_id = order_items.order_id
    INNER JOIN users ON orders.user_id = users.user_id
    INNER JOIN items ON order_items.item_id = items.item_id
GROUP BY orders.order_id
ORDER BY orders.order_id ASC;

--Q4
SELECT SUBSTRING(orders.order_time, 1, 7) AS '注文月',
       SUM(order_items.quantity) AS '注文数'
FROM orders
    INNER JOIN order_items ON orders.order_id = order_items.order_id
GROUP BY SUBSTRING(orders.order_time, 1, 7);

--Q5
SELECT SUBSTRING(orders.order_time, 1, 4) AS '注文年',
       SUM(order_items.quantity*items.price) AS '売上額'
FROM orders
    INNER JOIN order_items ON orders.order_id = order_items.order_id
    INNER JOIN items ON order_items.item_id = items.item_id
GROUP BY SUBSTRING(orders.order_time, 1, 4)
ORDER BY SUBSTRING(orders.order_time, 1, 4) ASC;

--Q6
SELECT SUM(order_items.quantity*items.price) AS '売上額'
FROM order_items INNER JOIN items ON order_items.item_id = items.item_id;

--Q7
SELECT item_category.name AS 'カテゴリ名', 
       SUM(order_items.quantity*items.price) AS '売上額'
FROM order_items
    INNER JOIN items ON items.item_id = order_items.item_id
    INNER JOIN item_category ON item_category.category_id = items.category_id
GROUP BY item_category.category_id
ORDER BY 売上額 DESC;

--Q8
SELECT items.name AS '商品名', 
       SUM(order_items.quantity*items.price) AS '売上額'
FROM order_items
    INNER JOIN items ON items.item_id = order_items.item_id
GROUP BY items.name
ORDER BY 売上額 DESC;

--Q9
SELECT item_category.name AS 'カテゴリ名', 
       SUM( 100*order_items.quantity*items.price/ 
            (SELECT SUM(order_items.quantity*items.price)
             FROM order_items INNER JOIN items ON order_items.item_id = items.item_id) ) AS '構成比（％）'
FROM order_items
    INNER JOIN items ON items.item_id = order_items.item_id
    INNER JOIN item_category ON item_category.category_id = items.category_id
GROUP BY item_category.category_id
ORDER BY 構成比（％） DESC;

--Q10
SELECT items.name AS '商品名', 
       SUM( 100*order_items.quantity*items.price/ 
            (SELECT SUM(order_items.quantity*items.price)
             FROM order_items INNER JOIN items ON order_items.item_id = items.item_id) ) AS '構成比（％）'
FROM order_items
    INNER JOIN items ON items.item_id = order_items.item_id
GROUP BY items.name
ORDER BY 構成比（％） DESC;