Student|Subject|Marks
aaa|eur|100
aaa|usd|90
aaa|eur|101
aaa|usd|80
aaa|eur|90
---------
bbb|usd|80
bbb|usd|100


##</code><code>##

aaa->eur->100 
aaa->eur->101
aaa->eur->90

aaa->usd->90 
aaa->usd->80

##</code><code>##

aaa,eur,sum(100,101,90)
aaa,usd,sum(90,80)

##</code><code>##

aaa,eur,100,sum(gg)
aaa,eur,100,sum(hh)
aaa,eur,101,sum(gf)
aaa,eur,101,sum(s)
aaa,eur,90,sum(dd)
aaa,eur,90,sum(sf)
aaa,usd,90,sum(eq)