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

Without having to add the group by clause, you can do the following:

Create a function to get the students count:

go
CREATE FUNCTION [dbo].GetStudentsCountByClass(@classId int) RETURNS INT
AS BEGIN
    declare @count as int

    select @count = count(*) from STUDENTS  
    where ClassId = @classId

    RETURN @count
END

then use it in your select statement

SELECT * , dbo.GetStudentsCountByClass(ClassId) AS StudentsCount
FROM Classes