why having came into existence wouldnot where have done all the work

Question

having clause

Answer 1

Where comes before the group by clause whereas having comes after the group by clause.. So, where cannot filter after the grouping whereas having can filter after the group by

Answer 2

some question cannot be answered unless you group them and apply group functions on them. so the developer made it easier for us by developing having clause. As Lahari said they are programed to work in that manner.