题解 | 商品销售排名

SELECT product_name, product_sales
FROM(
    SELECT l.product_id, product_name, COUNT(trace_id)*price AS product_sales
    FROM user_client_log l
    LEFT JOIN product_info p ON l.product_id = p.product_id
    WHERE step = 'select' AND pay_method IS NOT NULL
    GROUP BY l.product_id, product_name
    ORDER BY product_sales DESC
    LIMIT 2
) a;

奇葩的条件，WHERE step = 'select' AND pay_method IS NOT NULL，看题干完全想不到。