mysql - 如何高效的识别出异地代充的设备

Answer 1

谢谢邀请。用find_in_set函数试试看

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

不知道有没有写错，没有测试，但估计性能不会很好，毕竟涉及到disintct和group by操作。