How can I put "unassigned" when on delete in cascade instead of leaving it in null in an entity?

Question

Hello how can I put "unassigned" value on a table that has a join with cascade on delete with an other table instead of leaving it in null in an entity?

@OneToMany(fetch = FetchType.LAZY,cascade= CascadeType.ALL)
    @JoinColumn(name = "departmentName")