SQL Group By with multiple counts - sql

Question

I'm trying to group a list of services together along with the number of applicants in each service, but I also need a count on the status each applicant is in.
Applicants table
serviceID clientID applicantID status
----------------------------------------------------
1 41 1 1 (Processing)
1 41 16 1 (Processing)
1 41 15 2 (Ready)
2 41 12 1 (Processing)
2 41 18 3 (Complete)
Service table:
serviceID serviceName
--------------------------
1 Full Service
2 Part Service
Results need to look like:
serviceName totalApplicants processingCount readyCount completeCount
---------------------------------------------------------------------------
Full Service 3 2 1 0
Part Service 2 1 0 1
I've got the following, but it's returning the same count in each of the columns:-
SELECT
Services.serviceName,
(COUNT(Applicants.applicantID)) AS totalApplicants,
ISNULL(SUM(CASE WHEN Applicants.status = 1 THEN 1 ELSE 0 END), 0) AS processingCount,
ISNULL(SUM(CASE WHEN Applicants.status = 2 THEN 1 ELSE 0 END), 0) AS readyCount,
ISNULL(SUM(CASE WHEN Applicants.status = 3 THEN 1 ELSE 0 END), 0) AS completeCount
FROM
Applicants
LEFT JOIN
Services ON Applicants.serviceID = Services.serviceID
WHERE
Applicants.clientID = #CompanyID
GROUP BY
Services.serviceName

Answer 1

You can do conditional aggregation:
select
s.serviceName,
count(s.serviceID) totalApplicants,
sum(case when status = 1 then 1 else 0 end) processingCount,
sum(case when status = 2 then 1 else 0 end) readyCount,
sum(case when status = 3 then 1 else 0 end) completeCount
from service s
left join applicants a on a.serviceID = s.serviceID AND a.clientID = #CompanyID
group by s.serviceID, s.serviceName
The conditional expression use standard case expression; depending on the database that you are actually using, neater alternatives may exists.

Answer 2

Your query should be fine, but it can be simplified to:
SELECT s.serviceName,
COUNT(a.AppicantId) AS totalApplicants,
SUM(CASE WHEN a.status = 1 THEN 1 ELSE 0 END) AS processingCount,
SUM(CASE WHEN a.status = 2 THEN 1 ELSE 0 END) AS readyCount,
SUM(CASE WHEN a.status = 3 THEN 1 ELSE 0 END) AS completeCount
FROM Services s LEFT JOIN
Applicants a
ON a.serviceID = s.serviceID AND
a.clientID = #CompanyID
GROUP BY s.serviceName ;
Notes:
It looks like you want a row for every service, so that should be the first table in the LEFT JOIN.
Hence the filtering on the company goes into the ON clause.
Table aliases make the query easier to write and to read.
No ISNULL() is needed (and I prefer COALESCE() over ISNULL()).