使用FROM子句进行条件查询，该子句仅包含一个查询且不包含任何表

Question

我有以下查询，我不知道如何使用条件编写它。

SELECT questions_cnt, COUNT(*) users_cnt
FROM (
    SELECT COUNT(DISTINCT question) questions_cnt
    FROM UserAnswer
    GROUP BY user
) t
GROUP BY questions_cnt

我已经开始编写条件查询了。它看起来像以下

final DetachedCriteria subCriteria = DetachedCriteria.forClass(UserAnswer.class)
    .setProjection(
        Projections.projectionList()
            .add(Projections.alias(Projections.countDistinct("question"), "questions_cnt"))
            .add(Projections.groupProperty("user"))
    );
final DetachedCriteria criteria = DetachedCriteria.forClass(???);

我已经成功编写了子查询，但我不知道如何编写主查询。 DetachedCriteria需要创建实体类，但我的主查询不使用任何表。它使用from子句中的另一个查询作为其源。

UserAnswer entiry具有以下结构

@Entity
@Table(name = "user_answer")
public final class UserAnswer extends AbstractEntity {

    private static final long serialVersionUID = -3149418434619291049L;

    private Long id;
    private Date timestamp = new Date();
    private Answer answer;
    private Question question;
    private String userProvidedAnswer;
    private CourseSession courseSession;
    private User user;
    private Boolean checked;

    @Id
    @Override
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public Long getId() {
        return id;
    }

    @Override
    public void setId(Long id) {
        this.id = id;
    }

    @Version
    @Column(name = "timestamp", nullable = false)
    @Temporal(TemporalType.TIMESTAMP)
    public Date getTimestamp() {
        return timestamp;
    }

    public void setTimestamp(Date timestamp) {
        this.timestamp = timestamp;
    }

    @ManyToOne
    @ForeignKey(name = "fk__user_answer__answer")
    @OnDelete(action = OnDeleteAction.CASCADE)
    @JoinColumn(name = "answer_id")
    public Answer getAnswer() {
        return answer;
    }

    public void setAnswer(Answer answer) {
        this.answer = answer;
    }

    @ManyToOne
    @ForeignKey(name = "fk__user_answer__question")
    // @OnDelete(action = OnDeleteAction.CASCADE) // SQL Server does not support a cascade operation for this column
    @JoinColumn(name = "question_id", nullable = false)
    public Question getQuestion() {
        return question;
    }

    public void setQuestion(Question question) {
        this.question = question;
    }

    @Column(name = "user_provided_answer", length = 255)
    public String getUserProvidedAnswer() {
        return userProvidedAnswer;
    }

    public void setUserProvidedAnswer(String userProvidedAnswer) {
        this.userProvidedAnswer = StringUtils.trimToNull(userProvidedAnswer);
    }

    @ManyToOne
    @ForeignKey(name = "fk__user_answer__course_session")
    @JoinColumn(name = "course_session_id", nullable = false)
    public CourseSession getCourseSession() {
        return courseSession;
    }

    public void setCourseSession(CourseSession courseSession) {
        this.courseSession = courseSession;
    }

    @ManyToOne
    @ForeignKey(name = "fk__user_answer__user")
    @OnDelete(action = OnDeleteAction.CASCADE)
    @JoinColumn(name = "user_id", nullable = false)
    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    @Column(name = "is_checked")
    public Boolean getChecked() {
        return checked;
    }

    public void setChecked(Boolean checked) {
        this.checked = checked;
    }
}