Как узнать, что пользователь уже прочитал запись?

SELECT `id`, `name`, `total`, `rating`, `date_reg` FROM `users` WHERE `ref` > 0 AND `rating` > 0 AND `total` > 0 AND `date_reg` >= '$start_date'

SELECT `ref`, COUNT(*) AS total FROM users GROUP BY `ref`

SELECT
    t1.*, t2.name
FROM (
    SELECT
        REF, COUNT(id) AS COUNT
    FROM
        users
    GROUP BY
        REF
    HAVING 
        REF > 0
    ) AS t1
LEFT OUTER JOIN
    users AS t2
    ON
    t1.ref = t2.id
ORDER BY
    COUNT DESC

SELECT `ref`, COUNT(*) AS `total` FROM `users` WHERE `ref` > 0 AND `rating` > 0 AND `total` > 0 AND `date_reg` >= '$start_date' GROUP BY `ref` ORDER BY `total` DESC LIMIT 5

SELECT `ref`, COUNT(`ref`) AS `total` FROM `users` WHERE `ref` > 0 AND `rating` > 0 AND `total` > 0 AND `date_reg` >= 'дату пропишите сами' GROUP BY `ref` ORDER BY `total` DESC LIMIT 5

SELECT `ref`, COUNT(`ref`) AS `total` FROM `users` WHERE `ref` > 0 AND `rating` > 0 AND `total` > 0 AND `date_reg` >= 'дату пропишите сами' GROUP BY `ref`