-- create
CREATE TABLE student (
  Id INTEGER ,
  name TEXT
);

-- insert
INSERT INTO student VALUES (1, 'clark');
INSERT INTO student VALUES (2, 'Dave');
INSERT INTO student VALUES (3, 'Ava');

-- fetch 
CREATE TABLE backlog (
  student_Id INTEGER,
  subject_id TEXT NOT NULL
);

INSERT INTO backlog VALUES (null, 'abc123');
INSERT INTO backlog VALUES (3, 'def123');
INSERT INTO backlog VALUES (3, 'ijk123');
select name from student where id in (select student_id from backlog group by student_id having count(*) > 1);
-- SELECT t2.name from backlog t1 join student t2 on (t1.student_Id = t2.Id and t2.Id is not null) group by t1.student_Id having count(t2.name) > 1;
select name from student where id in (select student_id from backlog group by student_id having count(*) > 1);
SELECT t2.name  from backlog t1 join student t2 on t1.student_Id = t2.Id group by t1.student_Id having count(t2.name) > 1;
by