@Entity
public class Student{
	...
	@OneToMany(mappedBy="student")
	private List<Presentation> presentations;
	private String firstName;
	private int yearjoined;
	...
} 

@Entity
public class Presentation{
	...
	@ManyToOne
	@JoinColumn(name = "STUDENT_ID")
	private Student student;
	private String topic;
	...
} 

Student s = new Student(); // Empty costructor does nothing (ie. does not initialize presentations)
s.setId(1);
s.setYearjoined(100);
em.merge(s);

1) --SELECT ID, FIRSTNAME, LASTNAME, ROLLNUMBER, SCORE, DEPT, NUMBER, YEARJOINED FROM STUDENT WHERE (ID = ?)	-- bind => [1]

2) --SELECT ID, GRADED, MARKSOBTAINED, TOPIC, STUDENT_ID FROM PRESENTATION WHERE (STUDENT_ID = ?) -- bind => [1]

3) --UPDATE STUDENT SET FIRSTNAME = ?, LASTNAME = ?, ROLLNUMBER = ?, SCORE = ?, DEPT = ?, NUMBER = ?, YEARJOINED = ? WHERE (ID = ?) bind => [null, null, null, 0, null, null, 100, 1]

1) select student0_.id as id13_0_, student0_.dept as dept13_0_, student0_.number as number13_0_, student0_.yearjoined as yearjoined13_0_, student0_.firstname as firstname13_0_, student0_.lastname as lastname13_0_, student0_.rollnumber as rollnumber13_0_, student0_.score as score13_0_ from Student student0_ where student0_.id=?
2) update Student set dept=?, number=?, yearjoined=?, firstname=?, lastname=?, rollnumber=?, score=? where id=?