题目貌似是10天内的最高价和最低价么?
(select st.ID,st.Name,st.datum
form stock as st, stock as maxp
where st.preis=Max(maxp.preis) und datediff(tt-mm-yyyy,maxp.datum,getdate();)<=10)
UNION
(select st.ID,st.Name.stdatum
form stock as st, stock as minp
where st.preis=Min(minp.preis) und datediff(tt-mm-yyyy,minp.datum,getdate();)<=10)