SQL Server 2017

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CREATE TABLE dbo.SomeTableName
(
  Subject varchar(32),
  Semester tinyint,
  Attendee nvarchar(64)
);

INSERT dbo.SomeTableName(Subject, Semester, Attendee) VALUES
('ITB001', 1, N'John'),  
('ITB001', 1, N'Bob'),   
('ITB001', 1, N'Mickey'),
('ITB001', 2, N'Jenny'), 
('ITB001', 2, N'James'), 
('MKB114', 1, N'John'),  
('MKB114', 1, N'Erica'); 
7 rows affected

/* SQL Server 2017+ */

    SELECT Attendee, Semester, Subjects = STRING_AGG(Subject, ',')
      FROM dbo.SomeTableName
      GROUP BY Attendee, Semester;


Attendee
Semester
Subjects


Bob
1
ITB001

Erica
1
MKB114

John
1
MKB114,ITB001

Mickey
1
ITB001

James
2
ITB001

Jenny
2
ITB001


/* Older/unsupported versions */

    SELECT Attendee, Semester, Subjects = STUFF((
      SELECT ',' + ist.Subject
        FROM dbo.SomeTableName AS ist
        WHERE ist.Attendee = ost.Attendee
          AND ist.Semester = ost.Semester
        --GROUP BY ist.Subject
        FOR XML PATH(''), 
        TYPE).value(N'./text()[1]', N'varchar(max)'), 1, 1, '')
    FROM dbo.SomeTableName AS ost
    GROUP BY Attendee, Semester;


Attendee
Semester
Subjects


Bob
1
ITB001

Erica
1
MKB114

James
2
ITB001

Jenny
2
ITB001

John
1
ITB001,MKB114

Mickey
1
ITB001

Attendee	Semester	Subjects
Bob	1	ITB001
Erica	1	MKB114
John	1	MKB114,ITB001
Mickey	1	ITB001
James	2	ITB001
Jenny	2	ITB001