Select count from another table to each row in result rows

Question

Here are the tables:

CREATE TABLE [dbo].[Classes](
    [ClassId] [int] NOT NULL,
    [ClassName] [nvarchar](50) NOT NULL,
 CONSTRAINT [PK_Classes] PRIMARY KEY CL         


        

Answer 1

SELECT class.ClassId, count(student .StudentId) AS studentCount
FROM dbo.CLASSES class LEFT JOIN dbo.STUDENTS student ON (class.ClassId=student.ClassId)
GROUP BY class.ClassId