Untitled

-- 17. 
SELECT
    c.name AS customer_name,
    p.name AS product_name,
    oi.amount,
    oi.price
FROM
    orders o
JOIN order_items oi ON o.id = oi.order_id
JOIN customers c ON o.customer_id = c.id
JOIN products p ON oi.product_id = p.id;

-- 18.
SELECT
    c.name AS customer_name,
    SUM(oi.price) AS total_purchase
FROM
    customers c
JOIN orders o ON c.id = o.customer_id
JOIN order_items oi ON o.id = oi.order_id
GROUP BY
    c.id
ORDER BY
    total_purchase DESC
LIMIT 5;

-- 19. 
SELECT
    c.name AS customer_name,
    SUM(oi.price) AS total_purchase
FROM
    customers c
JOIN orders o ON c.id = o.customer_id
JOIN order_items oi ON o.id = oi.order_id
GROUP BY
    c.id
HAVING
    total_purchase > 10000;

-- 20.
SELECT
    e.name AS employee_name,
    SUM(oi.price) AS total_sales
FROM
    employees e
JOIN orders o ON e.id = o.employee_id
JOIN order_items oi ON o.id = oi.order_id
GROUP BY
    e.id
HAVING
    total_sales > (SELECT AVG(sales) FROM (SELECT e.id, SUM(oi.price) AS sales FROM employees e LEFT JOIN orders o ON e.id = o.employee_id LEFT JOIN order_items oi ON o.id = oi.order_id GROUP BY e.id) AS employee_sales);

-- 21. 
SELECT
    e.name AS employee_name
FROM
    employees e
LEFT JOIN orders o ON e.id = o.employee_id
WHERE
    o.id IS NULL;

-- แสดงลูกค้าที่ไม่มียอดซื้อ
SELECT
    c.name AS customer_name
FROM
    customers c
LEFT JOIN orders o ON c.id = o.customer_id
WHERE
    o.id IS NULL;

-- 22. 
SELECT
    c.name AS customer_name,
    MAX(oi.price) AS max_purchase_amount
FROM
    customers c
JOIN orders o ON c.id = o.customer_id
JOIN order_items oi ON o.id = oi.order_id
GROUP BY
    c.id
HAVING
    max_purchase_amount > (SELECT AVG(purchase_amount) FROM (SELECT c.id, MAX(oi.price) AS purchase_amount FROM customers c JOIN orders o ON c.id = o.customer_id JOIN order_items oi ON o.id = oi.order_id GROUP BY c.id) AS customer_purchases);

-- 23. 
SELECT
    c.name AS customer_name
FROM
    customers c
JOIN orders o ON c.id = o.customer_id
WHERE
    o.employee_id IS NULL
ORDER BY
    COUNT(o.id) DESC
LIMIT 1;

-- 24. 
SELECT
    c.name AS customer_name
FROM
    customers c
WHERE
    c.id NOT IN (SELECT DISTINCT o.customer_id FROM orders o JOIN order_items oi ON o.id = oi.order_id JOIN products p ON oi.product_id = p.id JOIN suppliers s ON p.supplier_id = s.id WHERE s.name = 'ไท เอฟเวอเรสต์');

-- 25. 
SELECT
    c.name AS customer_name
FROM
    customers c
JOIN orders o ON c.id = o.customer_id
JOIN order_items oi ON o.id = oi.order_id
JOIN products p ON oi.product_id = p.id
WHERE
    p.name IN ('น้ำดื่มตรา คชสาร', 'น้ำดื่มตรา แมมมอธ')
GROUP BY
    c.id
HAVING
    COUNT(DISTINCT p.id) = 2;

-- 26.
SELECT
    c.name AS customer_name
FROM
    customers c
JOIN orders o ON c.id = o.customer_id
JOIN order_items oi ON o.id = oi.order_id
JOIN products p ON oi.product_id = p.id
JOIN suppliers s ON p.supplier_id = s.id
WHERE
    s.name = 'ไท อาเซียน แอตแลนติก'
    AND c.id NOT IN (SELECT DISTINCT c.id FROM customers c JOIN orders o ON c.id = o.customer_id JOIN order_items oi ON o.id = oi.order_id JOIN products p ON oi.product_id = p.id JOIN suppliers s ON p.supplier_id = s.id WHERE s.name = 'ไท เอฟเวอเรสต์');