SELECT DISTINCT `a`.`Timestamp`, `a`.`OriginIP`,
    `a`.`User_browser`, `c`.`Activity_ID`, `c`.`DATA`
    from `Tomcat_server_logs` `a`
    INNER JOIN `user_activity` `c` ON
       `a`.`Timestamp`=`c`.`Timestamp`
       INNER JOIN
        (
          SELECT `Timestamp`, `Activity_ID`, `DATA`
          FROM `user_activity`
          GROUP BY `Timestamp`
        ) b ON c.Timestamp = b.Timestamp AND
          c.`Activity_ID` = b.`Activity_ID` AND
          c.`DATA` = b.`DATA`
   WHERE (c.`DATA` LIKE '%submit%') or (c.`DATA` LIKE '%uploadFile')
ORDER BY c.`Timestamp`;

...
    INNER JOIN `user_activity` `c` ON
       ((`a`.`Timestamp` <= ADDTIME(`c`.`Timestamp`,'0 0:0:4')
       AND (`a`.`Timestamp` >= SUBTIME(`c`.`Timestamp`,'0 0:0:4'))
       INNER JOIN
       ...