we also cannot use having without using group by.
this is false.... we can have a having clause without groupby clause.
having count(*) > 2;
this query provide the output as no.of rows if no.of rows in student table is grater than 2 otherwise result nothing printed.
SQL contains having clause without groupby clause is meaningless but VALID.
But note that, if aggregate operator uses attributes, then groupby clause must present.
we have to consider each clause separetely,
where clause doesn't support aggregate operators ===> option a and b are ruledout
option c and option d both are correct.