JPA @NamedQuery select @OneToMany object 类型

Question

假设我们有以下情况：A parent 有一个 children 的列表，而每个 children 是 "number" 或 "alphabet" 类型，并且我想 select parent

有一个或多个 "number" children 其 "number" 等于 42
根本没有 "number" children（但可能有 "alphabet" children）

我有以下最小示例，我已经解决了第一种情况，但不知道第二种情况，因为我假设我必须按 object 类型进行过滤，但我不确定这是否是仅通过 SQL 是否可行（我不想在 Java 中进行过滤以尽早减少相关实体的数量）。

Parent.java

import java.io.Serializable;
import java.util.List;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;

@Entity
@NamedQueries({
    @NamedQuery(name = "findWithNumberChildrenContainingNumber42", query = "SELECT nc.parent from NumberChild nc WHERE nc.number = 42"),
    @NamedQuery(name = "findWithoutNumberChildren", query = "?")
})
public class Parent implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @OneToMany(mappedBy = "parent")
    private List<Child> children;

    // ...
}

Child.java

import java.io.Serializable;
import javax.persistence.ManyToOne;
import javax.persistence.MappedSuperclass;

@MappedSuperclass
abstract class Child implements Serializable {

    @ManyToOne
    private Parent parent;

    // ...
}

数量Child.java

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class NumberChild extends Child {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private Integer number;

    // ...  
}

字母表Child.java

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class AlphabetChild extends Child {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String alphabet;

    // ...
}

Answer 1

原来之前的查询比必要的更复杂，所以这是我刚刚测试过的。

SELECT p FROM Parent p WHERE p NOT IN (SELECT nc.parent FROM NumberChild nc)

好吧，在我的测试中名称不同，但 Hibernate 的日志显示它确实生成了更有效的查询。

JPA @NamedQuery select @OneToMany object 类型

JPA @NamedQuery select by @OneToMany object type

java

jpa

one-to-many

jql

Parent.java

Child.java

数量Child.java

字母表Child.java