Question

所以我在描述后的猪中有以下数据结构：

    --------------------------------------------------------------------------------------------------------------------------------------------------------
| summed_hours_and_miles_by_driver     | group:int     | :bag{:tuple(driver_name:chararray)}             | total_hours:long     | total_miles:long     | 
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|                                      | 27            | {(Mark Lochbihler), ..., (Mark Lochbihler)}     | 220                  | 11006                | 
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这个想法是驱动程序名称（Mark Lochbihler）在一个元组包中被多次复制。我怎样才能将它限制为单个名称，如SQL中的DISTINCT？

Answer 1

使用Distinct，假设A是你的关系

<?xml version='1.0' encoding='UTF-8'?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
          http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">    
    <bean id="newUserEmail" class="demo.NewUserEmail">
        <property name="policyComponent" ref="policyComponent"/>
        <property name="nodeService" ref="nodeService"/>
        <property name="personService" ref="personService"/>
        <property name="passwordGenerator" ref="passwordGenerator"/>
        <property name="authenticationService" ref="authenticationService"/>
    </bean>
</beans>

如何从一包元组中提取出来？

1 个答案: