NOT DISTINCT заявка в mySQL

В описанието на колоната на вашата таблица с резултати не виждам minit, address and number of occurrences . Затова бих опростил избора ви на:

SELECT e1.ninumber,
       e1.fname,
       e1.lname,
       e1.superNiNumber,
FROM   employee AS e1,
       employee AS e2
WHERE  e1.dno = 8
       AND e1.superNiNumber = e2.ninumber
       AND e2.dno = 8
       and (select count(*) from employee e3
            where e3.superNiNumber = e1.superNiNumber) > 1;