Hibernate HQL 多对一连接

Posted 2023-04-14

【中文标题】Hibernate HQL 多对一连接

【英文标题】：Hibernate HQL many to one join

【发布时间】：2016-11-28 17:38:10

【问题描述】：

我在 mysql 中有 2 个表，blocked_histories 和 blocked_detail_histories。 block_detail_histories 表与 block_histories 具有多对一的休眠关系。表创建脚本如下所示

blocked_history

CREATE TABLE `blocked_histories` (
  `id` INT(11) NOT NULL AUTO_INCREMENT,
  `type` VARCHAR(32) NOT NULL,
  `no_ecash` varchar(13) NOT NULL,
  `cif` VARCHAR(32) DEFAULT NULL,
  `reason_id` INT(4) NOT NULL,
  `desc` TEXT,
  `status` VARCHAR(32) NOT NULL,
  `created_date` DATETIME NOT NULL,
  `created_by` VARCHAR(100) NOT NULL,
  `total_balance` DECIMAL(15,6) NOT NULL,
  `broker` int(11) NOT NULL,
  `blocked_id` INT(11) NOT NULL UNIQUE,
  `remark` text,
  PRIMARY KEY (`id`),
    CONSTRAINT `CUSTOMFIELD_ID_FK` FOREIGN KEY (`reason_id`) REFERENCES `custom_field_possible_values` (`id`)
)  ENGINE=INNODB AUTO_INCREMENT=312 DEFAULT CHARSET=latin1;

blocked_detail_histories

CREATE TABLE `blocked_detail_histories` (
  `id` INT(11) NOT NULL AUTO_INCREMENT,
  `blocked_id` INT(11) NOT NULL,
  `no_ecash` VARCHAR(13) DEFAULT NULL,
  `prev_group` INT(11) NOT NULL,
  `balance` DECIMAL(15,6) NOT NULL,
  PRIMARY KEY (`id`),
   KEY `BLOCKED_ID_FK` (`blocked_id`),
   CONSTRAINT `BLOCKED_ID_HISTORIES_FK` FOREIGN KEY (`blocked_id`) REFERENCES `blocked_histories` (`blocked_id`)
)  ENGINE=INNODB AUTO_INCREMENT=312 DEFAULT CHARSET=latin1;

hibernate 映射看起来像这样

blocked_history

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

    <class dynamic-insert="true" dynamic-update="true"
        name="nl.strohalm.cyclos.entities.groups.BlockedHistories"
        table="blocked_histories">
        <id name="id" type="long">
            <column name="id" sql-type="bigint" />
            <generator class="native" />
        </id>
        <property name="type" column="type" type="string" not-null="true" length="32" />
        <property name="noEcash" column="no_ecash" type="string" not-null="true" length="13" />
        <property name="cif" column="cif" type="string" length="32" />

        <!--  <property name="reasonId" column="reason_id" type="int" not-null="true" length="11" /> -->
        <many-to-one name="reasonId" class="nl.strohalm.cyclos.entities.customization.fields.CustomFieldPossibleValue">
            <column name="reason_id" sql-type="integer"></column>
        </many-to-one>

        <property name="desc" column="desc" type="text" not-null="true" />
        <property name="status" column="status" type="string" length="32" />
        <property name="createdDate" column="created_date" type="calendar" not-null="true" />
        <property name="createdBy" column="created_by" type="string" not-null="true" length="100"/>
        <property name="totalBalance" column="total_balance" type="big_decimal" not-null="true" precision="15" scale="6" />
        <property name="brokerId" column="broker" type="int" not-null="true" length="11" />
        <property name="remark" column="remark" type="text" />
        <property name="blockedId" column="blocked_id" type="int" not-null="true" length="11" />
    </class>

</hibernate-mapping>

blocked_detail_histories

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

    <class dynamic-insert="true" dynamic-update="true"
        name="nl.strohalm.cyclos.entities.groups.BlockedDetailHistories"
        table="blocked_detail_histories">
        <id name="id" type="long">
            <column name="id" sql-type="bigint" />
            <generator class="native" />
        </id>
        <many-to-one name="blockedHistories" class="nl.strohalm.cyclos.entities.groups.BlockedHistories">
            <column name="blocked_id" sql-type="integer"></column>
        </many-to-one>
        <property name="noEcash" column="no_ecash" type="string" not-null="true" length="13" />
        <property name="prevGroup" column="prev_group" type="int" not-null="true" length="11" />
        <property name="balance" column="balance" type="big_decimal" not-null="true" precision="15" scale="6" />
    </class>

</hibernate-mapping>

如您所见，blocked_detail 历史表与blocked_histories 表具有多对一关系（在“blockedHistories”列中）

我尝试运行一个简单的 mysql 查询来连接两个看起来像这样的表

select bh.created_date, bdh.no_ecash, bh.type,
    bh.cif, bh.desc, bh.reason_id,
    bh.status, bh.created_by, bh.remark
from blocked_detail_histories bdh
join blocked_histories bh 
where bdh.blocked_id=4;

上面的 mysql 查询工作正常，但是当我尝试将上面的 mysql 查询转换为 HQL 查询时，结果什么也没给我。HQL 看起来像这样（这里的“:id”是 java NamedParameters）

select bdh.blockedHistories.blockedId
from BlockedDetailHistories bdh"
join bdh.blockedHistories bh
where bh.blockedId = :id

我试过这个，但什么也没给我

select bh.createdDate, bdh.noEcash, bh.type,
bh.cif, bh.desc, bh.reasonId,
bh.status, bh.createdBy, bh.remark
from BlockedDetailHistories bdh
join bdh.blockedHistories bh
where bh.blockedId = :id

任何建议我在这里缺少什么？关系定义可能吗？还是别的什么？任何帮助将不胜感激:)

【问题讨论】：

SQL 查询对于联接似乎不正确。您应该使用“ON”子句而不是“where” 示例：SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate FROM Orders INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID; 来源：w3schools.com/sql/sql_join.asp

【参考方案1】：

不是 xml hibernate 映射方面的专家， 但是您是否为休眠实体类应用了获取类型， 如果你定义了这样，那么你可以重试上面的查询，如下所示（在惰性获取类型的情况下）

select bdh.blockedHistories.blockedId
from BlockedDetailHistories bdh
left join fetch bdh.blockedHistories bh
where bh.blockedId = :id