mysql - 如何高效的识别出异地代充的设备

Answer 1

Thanks for the invitation. Try using the find_in_set function

SELECT id FROM table WHERE find_in_set('EC:XX', mac) OR find_in_set('DD:XX', mac);

Answer 2

SELECT mac FROM (
SELECT DISTINCT mac, username FROM ORDER
) AS tmp
GROUP BY mac
having count(1) > 1

I don’t know if there are any writing errors. There is no test, but I guess the performance will not be very good. After all, it involves the disintct and group by operations.