package vac.entities;

import java.io.Serializable;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.JoinColumn;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.OneToOne;
import javax.persistence.OneToMany;
import javax.persistence.ManyToOne;
import javax.persistence.CascadeType;
import javax.persistence.FetchType;
import vac.entities.City;

@Entity
@Table(name = "AutoCards")
public class AutoCard implements Serializable
{
   @Id
   @GeneratedValue
   private Long id;

   @OneToOne
   private City city;

   public City getCity() {
      return city;
   }

   public void setCity(City city) {
      this.city = city;
   }

   public String getCityName()
   {
      getCity().setId(getCityID());
      return getCity().getCityName();
   }

   ...
   
   @Column(name = "CityID")
   private Integer cityID;

   ...getters and setters...
}

package vac.entities;

import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "Cities")
public class City implements Serializable
{
   @Id
   @GeneratedValue
   private Integer id;
   
   @Column(name = "CityName")
   private String cityName;
   
   @Column(name = "Visible")
   private Integer visible;

   ...etc...
}

java.sql.SQLException: Unknown column 'autocard0_.city_id' in 'field list'
   com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2975)
   com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1600)
   ....