Spring JPA Criteria Query group by with to_char 函数答案

【问题标题】：Spring JPA Criteria Query group by with to_char functionSpring JPA Criteria Query group by with to_char 函数
【发布时间】：2020-02-22 02:42:19
【问题描述】：

我正在尝试按日/月/年分组

Expression<String> expression = criteriaBuilder.function(
                            "to_char", String.class, root.get("reqDate"),
                            criteriaBuilder.parameter(String.class, "dateSegment"));

query.multiselect(
                criteriaBuilder.count(root).alias(FIELD_COUNT), expression.alias("reqDate"))
               .groupBy(expression);
entityManager.createQuery(query)
        .setParameter("dateSegment","MM-YYYY")
        .getResultList();

但这会引发一个错误，即选择字段必须出现在组中，这已经是，我检查了生成的 sql，它在 db 控制台中工作。但不是 JPA，我做错了什么？

生成的sql

select 
  count(shipment0_.shipment_pk_id) as col_0_0_, 
  to_char(
    shipment0_.requested_delivery_date_time, 
    ?
  ) as col_2_0_ 
from 
  shipment shipment0_ 
group by 
  to_char(
    shipment0_.requested_delivery_date_time, 
    ?
  )

有绑定

2019-10-28 09:20:05,891 TRACE [0.0-8080-exec-6 Wcl5M33fEZTS5iF Wcl5M33fEZTS5iF] - o.h.type.descriptor.sql.BasicBinder      : binding parameter [6] as [VARCHAR] - [MM-YYYY]
2019-10-28 09:20:05,891 TRACE [0.0-8080-exec-6 Wcl5M33fEZTS5iF Wcl5M33fEZTS5iF] - o.h.type.descriptor.sql.BasicBinder      : binding parameter [10] as [VARCHAR] - [MM-YYYY]

为什么它绑定为两个不同的参数？

日志

org.postgresql.util.PSQLException: ERROR: column "shipment0_.requested_delivery_date_time" must appear in the GROUP BY clause or be used in an aggregate function
  Position: 383
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2440) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2183) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:308) ~[postgresql-42.2.5.jar:42.2.5]
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:441) ~[postgresql-42.2.5.jar:42.2.5]

【问题讨论】：

请粘贴java堆栈跟踪错误信息

标签： hibernate group-by spring-data-jpa hibernate-criteria

【解决方案1】：

您的错误是您使用 criteriaBuilder.parameter(String.class, "dateSegment") 作为 DateTime 格式化程序。而不是它，您应该使用cb.literal("MM-YYYY")，然后一切都应该按预期工作。所以正确的代码如下：

Expression<String> expression = criteriaBuilder.function(
                            "to_char", String.class, root.get("reqDate"),
                            criteriaBuilder.literal("MM-YYYY"));

query.multiselect(
                criteriaBuilder.count(root).alias(FIELD_COUNT), expression.alias("reqDate"))
               .groupBy(expression);
entityManager.createQuery(query)
        .getResultList();

【讨论】：

【解决方案2】：

通过使查询看起来像来实现这一点

select 
  count(shipment0_.shipment_pk_id) as col_0_0_, 
  to_char(
    shipment0_.requested_delivery_date_time, 
    ?
  ) as col_2_0_ 
from 
  shipment shipment0_ 
group by 
  2

【讨论】：