石家庄停车位在线预约平台13

HQL多表查询

这里使用 多对多关系的用户表（user）和角色表（role）举例。
对应的实体类
User.java

public class User {

    private int uid;
    private String uname;
    private int uage;
    private String usex;

    private Set<Role> roleSet=new HashSet<>();


    public Set<Role> getRoleSet() {
        return roleSet;
    }

    public void setRoleSet(Set<Role> roleSet) {
        this.roleSet = roleSet;
    }

    public int getUid() {
        return uid;
    }

    public void setUid(int uid) {
        this.uid = uid;
    }

    public String getUname() {
        return uname;
    }

    public void setUname(String uname) {
        this.uname = uname;
    }

    public int getUage() {
        return uage;
    }

    public void setUage(int uage) {
        this.uage = uage;
    }

    public String getUsex() {
        return usex;
    }

    public void setUsex(String usex) {
        this.usex = usex;
    }
}

Role.java

public class Role {

    private int rid;
    private String rname;
    private int authority;
    private Set<User> userSet=new HashSet<User>();

    public int getRid() {
        return rid;
    }

    public void setRid(int rid) {
        this.rid = rid;
    }

    public String getRname() {
        return rname;
    }

    public void setRname(String rname) {
        this.rname = rname;
    }

    public int getAuthority() {
        return authority;
    }

    public void setAuthority(int authority) {
        this.authority = authority;
    }

    public Set<User> getUserSet() {
        return userSet;
    }

    public void setUserSet(Set<User> userSet) {
        this.userSet = userSet;
    }
}

    内连接

Query query=session.createQuery(“from User u inner join u.role”);
List<User> list=query.list();

返回的结果是数组

    迫切内连接

Query query=session.createQuery(“from User u inner join fetch u.role”);
List<User> list=query.list();


返回的结果是对象

左外连接

Query query=session.createQuery(“from User u left outer join u.role”);
List<User> list=query.list();