JPA Annotation for Relations

Support
#1

Hi community,

I dont understand the relationship principe of JPA.

There is OneToMany, ManyToOne, OneToMany and ManyToMany annotation.

If I use OneToMany and ManyToOne,

normally, I only “mark” one entity, the one, which contains “1” entity of other reference.

But for example in OneToOne annotation:

//Class Person
@OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL, optional = false, orphanRemoval = true)
Person personA; 


//Class Teacher 
@OneToOne(mappedBy="personA", cascade=CascadeType.ALL)
Teacher b;

Why does I have to mark the teacher class too?
Is this not enough?

//Class Person
@OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL, optional = false, orphanRemoval = true)
Person personA;

And how do I have to modify sql scripts?
Does I need a column of both?

Thanks a lot