题解 | 未下单用户登陆渠道统计

SELECT
    u.channel,
    CAST(SUM(CASE WHEN o.order_id IS NULL THEN 1 ELSE 0 END) AS SIGNED) AS cnt
FROM
    user_info AS u LEFT JOIN order_log AS o
    ON u.uid=o.uid
GROUP BY
    u.channel
ORDER BY
    cnt DESC,
    u.channel ASC
LIMIT 1;