How to apply unique constraints using annotation

Question

@Column(name = \"userId\")
    @UniqueConstraint
    private Integer userId;

I am using these annotation for entering data into database table. i want

Answer 1

Here's an example of how to use @UniqueConstraint:

@Entity
@Table(name = "contact", 
  uniqueConstraints = @UniqueConstraint(columnNames = {"name", "company_id"}))
public class Contact {
  ...
}

This specifies that the combination of the "name" column and the "company_id" column will be unique.