[nosoop]

Add a column last_day_claimed.

When the reward is claimed, set the account's last reward claim day to TO_DAYS(NOW());, then you can check that the daily reward for the day hasn't been claimed by selecting from the table WHERE last_day_claimed >= TO_DAYS(NOW()); (you'll get zero rows if the reward hasn't been claimed).

Daily rollover dependent on your MySQL instance, I think.

For SQLite, I think you can use cast(julianday('now') as int) instead.