Select a.cName, Min(a.dDate) as dDate,a.nBall
from (select cName,  min(nBall) over (partition by cName) as MinBall, dDate, nBall from tb_test1) a
where a.minball=a.nball
group by a.cname,a.nball

При равных минимальных оценках берем минимальную дату

Oracle:

Select a.cName, Min(a.dDate) as dDate,a.nBall
from (select cName,  min(nBall) over (partition by cName) as MinBall, dDate, nBall from tb_test1) a
where a.minball=a.nball
group by a.cname,a.nball

При равных минимальных оценках берем минимальную дату