Hibernate / JPA + Derby – SELECT语句在GROUP BY，ORDER BY或选择列表中包含太多项
我使用Hibernate与Derby DB进行JPA DB映射。 对于复杂的对象结构，我得到“org.apache.derby.client.am.SqlException：SELECT语句在GROUP BY，ORDER BY或选择列表中有太多项”：
org.apache.derby.client.am.SqlException: SELECT statement has too many items in GROUP BY, ORDER BY or select list. org.apache.derby.client.am.Statement.completeSqlca(Unknown Source) org.apache.derby.client.net.NetStatementReply.parsePrepareError(Unknown Source) org.apache.derby.client.net.NetStatementReply.parsePRPSQLSTTreply(Unknown Source) org.apache.derby.client.net.NetStatementReply.readPrepareDescribeOutput(Unknown Source) org.apache.derby.client.net.StatementReply.readPrepareDescribeOutput(Unknown Source) org.apache.derby.client.net.NetStatement.readPrepareDescribeOutput_(Unknown Source) org.apache.derby.client.am.Statement.readPrepareDescribeOutput(Unknown Source) org.apache.derby.client.am.PreparedStatement.readPrepareDescribeInputOutput(Unknown Source) org.apache.derby.client.am.PreparedStatement.flowPrepareDescribeInputOutput(Unknown Source) org.apache.derby.client.am.PreparedStatement.prepare(Unknown Source) org.apache.derby.client.am.Connection.prepareStatementX(Unknown Source) org.apache.derby.client.am.Connection.prepareStatement(Unknown Source) org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:505) org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:423) org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:139) org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1547) org.hibernate.loader.Loader.doQuery(Loader.java:673) org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:236) org.hibernate.loader.Loader.loadEntity(Loader.java:1860) org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:48) org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:42) org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:3044) org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:395) org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:375) org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:139) org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:195) org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:103) org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:878) org.hibernate.impl.SessionImpl.get(SessionImpl.java:815) org.hibernate.event.def.DefaultMergeEventListener.entityIsDetached(DefaultMergeEventListener.java:229) org.hibernate.event.def.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:120) org.hibernate.event.def.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:53) org.hibernate.impl.SessionImpl.fireMerge(SessionImpl.java:677) org.hibernate.impl.SessionImpl.merge(SessionImpl.java:661) org.hibernate.impl.SessionImpl.merge(SessionImpl.java:665) org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:228) sun.reflect.GeneratedMethodAccessor376.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:365) $Proxy74.merge(Unknown Source) sun.reflect.GeneratedMethodAccessor376.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) java.lang.reflect.Method.invoke(Unknown Source) org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:240) $Proxy41.merge(Unknown Source) 有没有人遇到这个问题，如果解决方案是什么？ 我在想
- 切换到MySQL
- 懒惰地加载一些属性（fetch = FetchType.LAZY）
- 重新设计数据库模式（现在可能很难，使用Hyperjaxb从XSD模式生成数据库，并且必须更改shemas）
您会选择哪种解决方案？ 你知道Derby对SQL语句有什么限制吗？
尝试使用show_sql=true doc进行调试
检查生成的SQL并尝试调试它。
我相信Derby在GROUP BY子句中允许大约32,000列。 ORDER BY和SELECT列表中指定的列有类似的限制。