为什么我用hibernate建表会出现如此诡异的情况？

Question

最近在学着用anotation配置hibernate，结果发现一些诡异的情况……
实体类：
[code="java"]
ackage com.yyz.beans;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name = "score")
public class Score {
private int sId;
private Course cou;
private Student stu;
private double score;

@Id
@GeneratedValue
public int getsId() {
    return sId;
}

public void setsId(int sId) {
    this.sId = sId;
}

public Score(Student s1, Course c1, double i) {
    this.stu=s1;
    this.cou=c1;
    this.score=i;
}

@ManyToOne
@JoinColumn(name = "course_id")
public Course getCou() {
    return cou;
}

public void setCou(Course cou) {
    this.cou = cou;
}

@ManyToOne
@JoinColumn(name = "student_id")
public Student getStu() {
    return stu;
}

public void setStu(Student stu) {
    this.stu = stu;
}

public double getScore() {
    return score;
}

public void setScore(double score) {
    this.score = score;
}

}

[/code]

然后我让hibernate自动帮我生成表，结果它给我来了这么个建表语句：
[code="sql"]
22:37:41,130 DEBUG SchemaExport:377 -
create table score (
sId integer not null,
score double precision not null,
course_id integer,
student_id integer not null auto_increment,
primary key (student_id, course_id)
)
[/code]
明显我指定的主键是sid，为什么生成的建表语句里course_id和student_id为联合主键呢？
明显我设置了sid为自增长，为什么生成的建表语句里student_id成了自增长字段呢？

Answer 1

你是不是还有其他的表和这个表有关系．单独的话　应该不会这样．