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 c.ClassId,C.ClassName,COUNT(*) [Number of students]
 from Classes C,Students S
 where c.ClassId=S.ClassId
 group by C.ClassId,C.ClassName