具有复合主键查询的JPA COUNT无效

Question

在我的数据库中,我有一个表(默认值),当我从表生成一个实体时,我得到这两个类:

@Entity
public class Defaults implements Serializable {
    private static final long serialVersionUID = 1L;
    @EmbeddedId
    protected DefaultsPK DefaultsPK;
    @Column(name = "ERTEK")
    private String ertek;

    getter/setter...
}

@Embeddable
public class DefaultsPK implements Serializable {
    @Basic(optional = false)
    @Column(name = "VALUE_1")
    private String value1;
    @Basic(optional = false)
    @Column(name = "TYPE")
    private String type;
    @Basic(optional = false)
    @Column(name = "VALID_FROM")
    @Temporal(TemporalType.TIMESTAMP)
    private Date validFrom;
    @Basic(optional = false)
    @Column(name = "VALID_TO")
    @Temporal(TemporalType.TIMESTAMP)
    private Date validTo;

    getter/setter...
}

这就是为什么因为主键包含值.我想计算表中的所有行,所以我使用这段代码:

String sql = "SELECT COUNT(d) FROM Defaults d";
Query q = em.createQuery(sql);
long count = (long)q.getSingleResult();

但是我收到了这个错误:

org.hibernate.exception.SQLGrammarException: could not execute query
...
java.sql.SQLSyntaxErrorException: ORA-00907: The right expression is missing from the arithmetic expression

问题是什么？与其他实体的其他计数查询正在运行.

我正在使用休眠.

Answer 1

使用count(d.ertek)或count(d.id)代替count(d).当您的实体具有复合主键时,可能会发生这种情况.