【发布时间】：2016-10-13 06:52:41
【问题描述】：
我有表A，它与表B 有关系，为一对多。
我想要做的是从表A 和加入选定的结果表B 中使用іщьу 限制进行选择。
所以我遇到了一个问题，如何以正确的方式在休眠中做到这一点？
典型的Criteria.selectMaxResults 这不是我需要的，因为限制将在加入后接受，而不是从表A 中获取 10 个不同的行，例如，我会从表“A”中得到 1 行，加入 10表B 中的不同行。
(1) 那么最好的方法是什么？在一个查询中从A 中仅选择唯一行，在另一个查询中使用连接B 从A 中选择？
一般来说，在原生 SQL 语言上，我希望执行下一个查询：
String sQuery = SELECT a.*,b* FROM (SELECT * FROM parentTable WHERE c.id=777 LIMIT 0,10) AS a, b.* WHERE a.id=b.a_id;
因此，根据休眠教程和文档，我尝试使用session.createSQLQuery(sQuery)。我的方法看起来是这样的：
@Override
@Transactional
public List<VocabularyWord> getWords(int vocId, int firstResult, int pageSize) {
Session s = this.template.getSessionFactory().getCurrentSession();
SQLQuery query = s.createSQLQuery("SELECT {vW.*}, m.* FROM (SELECT * FROM vocabulary_words AS vw WHERE vw.vocabulary_id=:id LIMIT :from,:size) AS vW, meaning AS m WHERE vW.id=m.vocabulary_words_id;");
query.setInteger("id", vocId);
query.setInteger("from", firstResult);
query.setInteger("size", pageSize);
query.addEntity("vW", VocabularyWord.class);
query.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY);
// If unccoment the next word I get error: Column 'id1_1_1_' not found. But as I'have understood I don't need this.
// query.addEntity("m", Meaning.class);
List l = query.list();
return l;
}
这个方法返回的正是我想要的。但是要返回此结果，休眠会执行大量查询。 （他尝试做类似（1）的事情？）。恰好Hibernate 执行 5 个下一个查询：
Hibernate:
SELECT
vW.id as id1_7_0_,
vW.original_text as original2_7_0_,
vW.transcription as transcri3_7_0_,
vW.vocabulary_id as vocabula4_7_0_,
m.*
FROM
(SELECT
*
FROM
vocabulary_words AS vw
WHERE
vw.vocabulary_id=? LIMIT ?,?) AS vW,
meaning AS m
WHERE
vW.id=m.vocabulary_words_id;
Hibernate:
select
meaning0_.vocabulary_words_id as vocabula5_1_0_,
meaning0_.id as id1_1_0_,
meaning0_.id as id1_1_1_,
meaning0_.definition as definiti2_1_1_,
meaning0_.example as example3_1_1_,
meaning0_.translation as translat4_1_1_,
meaning0_.vocabulary_words_id as vocabula5_1_1_,
meaning0_.w_type as w_type6_1_1_
from
meaning meaning0_
where
meaning0_.vocabulary_words_id=?
Hibernate:
select
meaning0_.vocabulary_words_id as vocabula5_1_0_,
meaning0_.id as id1_1_0_,
meaning0_.id as id1_1_1_,
meaning0_.definition as definiti2_1_1_,
meaning0_.example as example3_1_1_,
meaning0_.translation as translat4_1_1_,
meaning0_.vocabulary_words_id as vocabula5_1_1_,
meaning0_.w_type as w_type6_1_1_
from
meaning meaning0_
where
meaning0_.vocabulary_words_id=?
Hibernate:
select
meaning0_.vocabulary_words_id as vocabula5_1_0_,
meaning0_.id as id1_1_0_,
meaning0_.id as id1_1_1_,
meaning0_.definition as definiti2_1_1_,
meaning0_.example as example3_1_1_,
meaning0_.translation as translat4_1_1_,
meaning0_.vocabulary_words_id as vocabula5_1_1_,
meaning0_.w_type as w_type6_1_1_
from
meaning meaning0_
where
meaning0_.vocabulary_words_id=?
Hibernate:
select
meaning0_.vocabulary_words_id as vocabula5_1_0_,
meaning0_.id as id1_1_0_,
meaning0_.id as id1_1_1_,
meaning0_.definition as definiti2_1_1_,
meaning0_.example as example3_1_1_,
meaning0_.translation as translat4_1_1_,
meaning0_.vocabulary_words_id as vocabula5_1_1_,
meaning0_.w_type as w_type6_1_1_
from
meaning meaning0_
where
meaning0_.vocabulary_words_id=?
我的VocabularyWord 实体：
public class VocabularyWord implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "id", updatable = false, nullable = false)
private int id;
@Column(name = "vocabulary_id", updatable = false, nullable = false)
private int vocId;
@Column(name = "original_text", nullable = false)
private String originalText;
@Column(name="transcription", nullable = true)
private String transcription;
@OneToMany (mappedBy = "vocWord", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private Set<Meaning> meaning;
// + getters and setters
}
我的意义实体：
public class Meaning implements Serializable {
@Id
@Column(name = "id", updatable = false, nullable = false)
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;
@JsonIgnore
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "vocabulary_words_id", nullable = false, updatable = false)
private VocabularyWord vocWord;
@JsonIgnore
@Column(name = "vocabulary_words_id", updatable = false, insertable = false)
private int vocWordId;
@Column(name = "w_type", nullable = true, unique = false)
private String wType;
@Column(name = "example", nullable = true, unique = false)
private String example;
@Column(name = "definition", nullable = true, unique = false)
private String definition;
@Column(name = "translation", nullable = true, unique = false)
private String translation;
//+ getters and setters
}
我该如何解决这个问题？或者，我是否选择了其他方式来实现该查询？
我将不胜感激任何帮助、建议、想法和相关链接。提前致谢。
【问题讨论】：
标签： java mysql spring hibernate