sql query with percent and aggregation functions - sql

Question

I'm trying to write a sql query where I need number of scores > 3 by county, then for counties on that list I need to produce a percentage of rooms with scores < 3. So I need three columns, County Name, # of scores > 3 by county, % of rooms with scores < 3 by county
SELECT County = c.Description, [Score > 3] = count(s.Score),
((select count(room.Name) where s.Score< 3) /( select count(room.Name) ) * 100)
FROM Sites AS s
inner join Profiles as p on s.Profile_Id = p.Id
inner join Counties as c on p.County_Id = c.Id
inner join Rooms as room on s.Id = room.Site_Id
where s.Score > 3
Group By c.Description

Answer 1

I think you are over complicating the issue, rather than subselects you can just limit the data returned by using the HAVING clause, then use CASE in the COUNT:
SELECT County = c.Description,
[Score > 3] = COUNT(CASE WHEN Sites.Score > 3 THEN 1 END),
[% Score < 3] = 100.0 * COUNT(CASE WHEN Sites.Score < 3 THEN 1 END) / COUNT(1)
FROM Sites
INNER JOIN Profiles
ON Sites.Profile_Id = Profiles.Id
INNER JOIN Counties
ON Profiles.County_Id = Counties.Id
INNER JOIN Rooms
ON Sites.Id = Rooms.Site_Id
GROUP BY c.Description
HAVING COUNT(CASE WHEN Sites.Score > 3 THEN 1 END) > 0;
Demo on SQL Fiddle
EDIT
SELECT County = c.Description,
[Score > 3] = COUNT(CASE WHEN Sites.Score > 3 THEN 1 END),
[% Score < 3] = 100.0 * SUM(CASE WHEN Sites.Score < 3 THEN 1 END) / COUNT(*),
[Score > 3] = SUM(CASE WHEN Sites.Score > 3 THEN RoomCount ELSE 0 END),
[% Score < 3] = 100.0 * SUM(CASE WHEN Sites.Score < 3 THEN RoomCount ELSE 0 END) / SUM(RoomCount)
FROM Sites
INNER JOIN Profiles
ON Sites.Profile_Id = Profiles.Id
INNER JOIN Counties
ON Profiles.County_Id = Counties.Id
INNER JOIN
( SELECT Site_Id, RoomCount = COUNT(*)
FROM Rooms
GROUP BY Site_Id
) Rooms
ON Sites.Id = Rooms.Site_Id
GROUP BY c.Description
HAVING COUNT(CASE WHEN Sites.Score > 3 THEN 1 END) > 0;

Answer 2

Use Cast
SELECT County = c.Description, [Score > 3] = count(s.Score),
( Cast(select count(room.Name) where s.Score < 3 ) as float / ( select count(room.Name) ) * 100)
FROM Sites AS s
inner join Profiles as p on s.Profile_Id = p.Id
inner join Counties as c on p.County_Id = c.Id
inner join Rooms as room on s.Id = room.Site_Id
where s.Score > 3
Group By c.Description

Answer 3

[Score > 3] = count(s.Score)
...
where s.Score > 3
Both statements are not needed. In fact your Where clause limits all operations to s.score >3, which is not ideal when you are also trying to pull data from scores <3.
If you are trying to count both the cases where s.Score>3 and where it is <3, you need to use the CASE statement
SELECT SUM(CASE WHEN s.score < 3 THEN 1 ELSE 0 END) AS Hiscores,
SUM(CASE WHEN s.score > 3 THEN 1 ELSE 0 END) /count(s.scores) AS percentLowScores
This should do it
SELECT c.Description County,
SUM(CASE WHEN s.score < 3 THEN 1 ELSE 0 END) AS Hiscores,
SUM(CASE WHEN s.score > 3 THEN 1 ELSE 0 END) /count(s.scores) AS percentLowScores
FROM Sites AS s
inner join Profiles as p on s.Profile_Id = p.Id
inner join Counties as c on p.County_Id = c.Id
inner join Rooms as room on s.Id = room.Site_Id
Group By c.Description