我有两个扩展基类的类。
问题.java

@Entity
@Table(name="question")
@Access(value = AccessType.FIELD)
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Questions{

    private static final long serialVersionUID = 1L;

    private String qid;

    @Column(name="addedtime")
    private String addedtime;

    @Column(name="qlang")
    private String qlang;

    @Id
    @Column(name="qid")
    @GeneratedValue(generator = "uuid2")
    @GenericGenerator(name = "uuid2", strategy = "uuid2")
    @Access(value = AccessType.PROPERTY)
    public String getQid() {
        return qid;
    }

    public void setQid(String qid) {
        this.qid = qid;
    }

    @Access(value = AccessType.PROPERTY)
    public String getAddedtime() {
        return addedtime;
    }

    public void setAddedtime(String addedtime) {
        this.addedtime = addedtime;
    }

    @Access(value = AccessType.PROPERTY)
    public String getQlang() {
       return qlang;
    }

    public void setQlang(String qlang) {
       this.qlang = qlang;
    }
}

mcq.java，twomarkq.java—这两个类都扩展了question.java。
mcq.java文件

@Entity
@Table(name="MCQ")
@Access(value = AccessType.FIELD)
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class MCQ extends Questions implements Serializable{

    @Column(name="option_1")
    @Access(value = AccessType.FIELD)
    private String option_1;

    @Access(value = AccessType.PROPERTY)
    public String getOption_1() {
        return option_1;
    }

    public void setOption_1(String option_1) {
        this.option_1 = option_1;
    }

    @Column(name="option_2")
    @Access(value = AccessType.FIELD)
    private String option_2;

    @Access(value = AccessType.PROPERTY)
    public String getOption_2() {
        return option_2;
    }

    public void setOption_2(String option_2) {
        this.option_2 = option_2;
    }

}

twomarkq.java文件

@Entity
@Table(name="TwoMarkQ")
@Access(value = AccessType.FIELD)
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class TwoMarkQ extends Questions implements Serializable{

    @Column(name="option_1")
    @Access(value = AccessType.FIELD)
    private String option_1;

    @Access(value = AccessType.PROPERTY)
    public String getOption_1() {
        return option_1;
    }

    public void setOption_1(String option_1) {
        this.option_1 = option_1;
    }

    @Column(name="option_2")
    @Access(value = AccessType.FIELD)
    private String option_2;

    @Access(value = AccessType.PROPERTY)
    public String getOption_2() {
        return option_2;
    }

    public void setOption_2(String option_2) {
        this.option_2 = option_2;
    }

}

这三个表都Map到mysql数据库中的唯一表。
下面是每个表的show create table的结果

create table `question` (
  `qid` varchar(48) COLLATE utf8mb4_unicode_ci NOT NULL,
  `addedtime` datetime(6) NOT NULL DEFAULT CURRENT_TIMESTAMP(6),
  `qtype` varchar(32) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `qlang` varchar(48) COLLATE utf8mb4_unicode_ci NOT NULL,
   PRIMARY KEY (`qid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

create table `MCQ`(
`qid` varchar(48) COLLATE utf8mb4_unicode_ci NOT NULL,
`option_1` bigint(20) DEGAULT `0`,
`option_2` bigint(20) DEGAULT `0`,
PRIMARY KEY (`qid`),
CONSTRAINT `mcq_ibfk1` FOREIGN KEY (`qid`) REFERENCES `question` (`qid`)
)ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

create table `TwoMarkQ`(
`qid` varchar(48) COLLATE utf8mb4_unicode_ci NOT NULL,
`option_1` bigint(20) DEGAULT `0`,
`option_2` bigint(20) DEGAULT `0`,
PRIMARY KEY (`qid`),
CONSTRAINT `two_markq_ibfk1` FOREIGN KEY (`qid`) REFERENCES `question` (`qid`)
)ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci

在一个dao类中，sql查询是这样的（sql查询是针对派生类的）

Query query = session.createQuery("select q.qid, q.qtype from Questions q where q.qlang=:lang ORDER BY q.addedtime ASC");
            query.setParameter("lang", lang);
            query.setFirstResult(startingRow).setMaxResults(10);
            result = (List<Questions>) query.list();

错误发生在上面的行中 result = (List<Questions>) query.list(); com.mysql.jdbc.exceptions.jdbc4.mysqlsyntaxerrorexception:字段列表中的未知列“qid”
问题1）为什么我会 com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'addedtime' in 'field list' 如何修复？
请帮忙。在这上面敲了三天。
ps：我使用的是Hibernate4.3.5.final版本
ps：这是生成的查询

select questions0_.qid as col_0_0_, questions0_.qtype as col_1_0_ from ( select qid, addedtime, qlang, qtype, null as option_1, null as option_2 as class_ from MCQ union  select qid, addedtime, qlang, qtype, null as option_!, null as option_2 as class_ from TwoMarkQ)  questions0_ where questions0_.qlang=? order by questions0_.addedtime ASC limit ?

自从 Query query = session.createQuery("select q.qid, q.qtype from Questions q where q.qlang=:lang ORDER BY q.addedtime ASC"); 在基类上，看起来它正在与所有子类进行并集，子类没有addedtime列。我只是在猜测。