Sql server - Using aggregate functions in where clause - sql-server

Question

I am working on a sql query for Transport business, this query when executed should get the drivers information who got more than 20% star rating(5*) rating from his customers in last 30 days... also that should be a minimum of 5 trips..
Lets say if a driver completed 100 trips in last 30 days and he received 30 star rating (5*) feedback then this Driver and all his star (5*) Trips information should be retrieved by the query..this driver has completed more than 20% 5 star trips
select tr.[TripId], tr.[DriverId], tr.[Rating], dr.[DriverName]
from tblTripInfo
left outer join tblDriver dr
on tr.[DriverId] = dr.[DriverId]
where tr.[Rating] = 5 and tr.[TripDate] >= GetDate() - 30
the above query gets all the information of trips and driver who got 5* ratings in last 30 days, i want to get only those who have minimum of 20% 5* trips out of their total trips and that should me minimum of 5 trips
Initially i wanted to get only DriverId's who met the above condition and the below query worked
select DriverId,
count(case when Rating = 5 then DriverId end) as TotalStars,
100.0 * avg(case when Rating = 5 then 1.0 else 0 end) as Average5Stars
from tblTripInfo
where TripDate >= GetDate() - 30
group by DriverId
having
count(case when Rating = 5 then DriverId end) > 10
and
100.0 * avg(case when Rating = 5 then 1.0 else 0 end) > 25
But now i want to get all the information like tripId, driverName, trip date of those 5* trips as well

Answer 1

You need something in the line of this:
WITH TotalTrips as (
SELECT Count() as TotalTrips,
DriverId
FROM tblTripInfo
GROUP BY DriverId
)
SELECT DriverId,
count(case when Rating = 5 then DriverId end) as Total5StarTrips,
100.0 * avg(case when Rating = 5 then 1.0 else 0 end) as Average5Stars
FROM tblTripInfo t1
JOIN TotalTrips t2
ON t1.DriverId = t2.DriverId
AND t2.TotalTrips > 5 --more than 5 trips
where TripDate >= GetDate() - 30
group by DriverId
HAVING COUNT(case when Rating = 5 then DriverId end) / t2.TotalTrips > 0.2 --more than 20% 5-starred trips
No need of complicated logic if you can use some SubQuery for simplicity.