SQL Server 2008 :: Query Within A Query?

I have a query:

SELECT CONVERT(char(3), dbo.tblCourses.CourseDate, 0) AS Month, YEAR(dbo.tblCourses.CourseDate) AS Year, SUM(CASE WHEN a.AttendanceStatus IN (9)
THEN 1 ELSE 0 END) AS [City CCG Attended], SUM(CASE WHEN a.AttendanceStatus IN (3) THEN 1 ELSE 0 END) AS [City CCG DNA],
SUM(CASE WHEN a.AttendanceStatus IN (7) THEN 1 ELSE 0 END) AS Cancelled, gp.CCGRegion
FROM dbo.tblGP_Practices AS gp INNER JOIN

[Code] ....

I wanted to add anohter column where it counts the results of the followign query:

SELECT dbo.tblPatient.NHSnumber, dbo.tblPatient.DateOfBirth, dbo.tblPatient.DateReferralReceived, dbo.tblGP_Practices.OrganisationCode
FROM dbo.tblPatient INNER JOIN
dbo.tblGP_PatientLink ON dbo.tblPatient.PatientID = dbo.tblGP_PatientLink.PatientID INNER JOIN
dbo.tblGP_Practices ON dbo.tblGP_PatientLink.GPPracticeID = dbo.tblGP_Practices.GPPracticeID LEFT OUTER JOIN
dbo.tblAppointments ON dbo.tblPatient.PatientID = dbo.tblAppointments.PatientID
WHERE (dbo.tblAppointments.PatientID IS NULL)

is this possible?