引起：java.sql.SQLException：找不到列'id'

Question

我想获取一些字段，然后将其设置为我的Test.entity。我的SQL查询：

   query = "SELECT t.id as tId, t.test_name, t.duration, q.id as qId, " + 
        "q.question as question, q.is_multichoice as is_multichoice, " + 
        "q.is_open as is_open, a.id as aId, a.answer_text as answer_text FROM result r " + 
        "JOIN test t ON r.test_id = t.id " + 
        "JOIN user u ON r.user_id = u.id " + 
        "JOIN question q ON t.id = q.test_id JOIN answer a ON q.id = a.question_id " + 
        "WHERE t.id = :testId AND u.id = :userId AND r.permission = :permissionId " + 
        "AND q.archived = false AND a.archived = false", resultClass = com.bionic.entities.Test.class) 

测试实体：

public class Test { 
@Id 
@Column(name = "id") 
@GeneratedValue(strategy = GenerationType.AUTO) 
private long id; 
@Column(name = "duration", nullable = false) 
private int duration; 
@Column(name = "test_name", nullable = false, unique = true) 
private String testName; 
@Column(name = "archived", nullable = false) 
private boolean archived; 
@OneToMany(mappedBy = "test", fetch = FetchType.EAGER) 
private Set<Question> questions; 
@ManyToMany(mappedBy = "tests") 
private Set<User> users; 

问题实体：

public class Question { 
@Id 
@Column(name = "id") 
@GeneratedValue(strategy = GenerationType.AUTO) 
private long id; 
@Column(name = "is_multichoice", nullable = false) 
private boolean isMultichoice; 
@Column(name = "is_open", nullable = false) 
private boolean isOpen; 
@Column(name = "picture") 
private String picture; 
@Column(name = "question") 
private String question; 
@ManyToOne 
@JoinColumn(name = "test_id", nullable = false) 
private Test test; 
@Column(name = "archived", nullable = false) 
private boolean isArchived; 
@OneToMany(mappedBy = "question", fetch = FetchType.EAGER) 
private Set<Answer> answers; 

答实体：

public class Answer { 
@Id 
@Column(name = "id") 
@GeneratedValue(strategy = GenerationType.AUTO) 
private long id; 
@Column(name = "answer_text", nullable = false) 
private String answerText; 
@Column(name = "mark", nullable = false) 
private int mark; 
@ManyToOne 
@JoinColumn(name = "question_id") 
private Question question; 
@Column(name = "picture") 
private String picture; 
@Column(name = "archived", nullable = false) 
private boolean isArchived; 

然而，执行这个查询后，我得到exeption：

Caused by: java.sql.SQLException: Column 'id' not found. 

DAO.class：

public Test getCurrentTest(long id, long testId, long permissionId) { 
    Query query = em.createNamedQuery("getCurrentTestById"); 
    query.setParameter("userId", id); 
    query.setParameter("testId", testId); 
    query.setParameter("permissionId", permissionId); 
    return (Test) query.getSingleResult(); 
} 

我到底做错了什么？

Answer 1

您的查询不会返回名为id的字段。它具有名为aId, qId, and tId的字段。

您需要在实体中使用正确的列名称。例如，在您的Test实体中，您声明了一个名为id的列。除了你的查询没有返回一个名为id的列，它将返回一个名为tId的列。请参阅下面的示例，了解需要更改的内容。

public class Test { 
@tId 
@Column(name = "tId") 
@GeneratedValue(strategy = GenerationType.AUTO) 
private long tId; 
....