SELECT
    order_id,
    order_date,
    IF(YEAR(order_date) = YEAR(NOW()),
    ‘Active’,
    ‘Archived’) AS category
    FROM orders

    练习题：
    image.png
    SELECT
    p.product_id,
    p.name,
    COUNT() AS orders
    IF(COUNT(    ) > 1,
    ‘Many times’,
    ‘Once’) AS frequence
    FROM products p
    JOIN order_items o
    ON p.product_id = o.product_id
    GROUP BY p.product_id, p.name