u can implement the where clause in backend, and if u want to implement some dondition to filter ur value in chart then u can do it in chart expression like u can write in expression defination
sum(if(Value>1,Value)) or any other expression.
even u can ristruct ur dimensions by adding the condition in Dimension>> Add calculated Dimensions.
I can help better if u can tell what condition u want to implement to ristrict value or
on what basis u want to ristrict the values.