如何使用JPA求和

编程问答 2022-08-11

问题描述

我在sql和类似JPA的代码之间转换的背景不多，所以我想知道如何将以下内容转换为JPA语法？还是有可能？预先感谢。

SELECT DLR_CD,COUNT(*),SUM(CASE WHEN CMplt_DT='0001-01-01' THEN 1 END),SUM(CASE WHEN CMplt_DT!='0001-01-01' THEN 1 END),SUM(CASE WHEN YEAR(CMplt_DT) = YEAR(CURRENT DATE)-1 THEN 1 END),SUM(CASE WHEN YEAR(CMplt_DT) = YEAR(CURRENT DATE) THEN 1 END),SUM(CASE WHEN (CMplt_DT IS NULL OR CMplt_DT='0001-01-01') THEN A.RPR_LBR_HR ELSE 0 END)
FROM <db2 table 1> A
join <db2 table 2> B
on ANUN_IND='A'
AND B.PIP_PSP_NO=A.PIP_PSP_NO
--OPTIONAL ParaMS GO HERE
GROUP BY DLR_CD
FOR FETCH ONLY WITH UR;

编辑：使用完整的，几乎未修改的查询进行更新。

解决方法

使用标准api，它看起来像这样：

    CriteriaBuilder cb = entityManager.getCriteriaBuilder();
    CriteriaQuery<YourPojo> cq = cb.createQuery(YourPojo.class);
    
    Root<Entity1> root = cq.from(Entity1.class);
    Join<Entity1,Entity2> join = root.join(Entity1_.entity2,JoinType.LEFT);
    /* 
     * the join by ID is implicit when using the .join method,the second
     * condition is added as follows (Since you don't indicate the alias,* I assume it is a field from table 2):
     */
    join.on(cb.equal(join.get(Entity2_.anunInd),'A'));
    
    Calendar dayOne = Calendar.getInstance();
    dayOne.set(1,1);
    
    //Expression for first and second sum case
    Expression<Long> caseDate = cb.<Long>selectCase().when(cb.equal(root.get(Entity1_.cmpltDt),dayOne.getTime()),1L).otherwise(0L);
    Expression<Long> sumDate = cb.sum(caseDate);
    
    //Expression for third sum case
    Expression<Long> caseDateWithYearM1 = cb.<Long>selectCase().when(
            cb.equal(cb.function("YEAR",Long.class,root.get(Entity1_.cmpltDt)),cb.sum(cb.function("YEAR",cb.literal(new Date())),-1)),1L).otherwise(0L);
    Expression<Long> sumDateWithYearM1 = cb.sum(caseDateWithYearM1);
    
    //Expression for fourth sun case
    Expression<Long> caseDateWithYear = cb.<Long>selectCase().when(
            cb.equal(cb.function("YEAR",cb.function("YEAR",cb.literal(new Date()))),1L).otherwise(0L);
    Expression<Long> sumDateWithYear = cb.sum(caseDateWithYear);

    Expression<Long> caseNew = cb.<Long>selectCase().when(cb.or(
      cb.equal(root.get(Entity1_.cmpltDt),cb.equal(root.get(Entity1_.cmpltDt),dayOne.getTime())),root.get(Entity1_.rprLbrHr)).otherwise(0L);

    Expression<Long> sumNew = cb.sum(caseNew);

    
    cq.multiselect(
            root.get(Entity1_.dlrCd),cb.count(root.get(Entity1_.dlrCd)),sumDate,sumDateWithYearM1,sumDateWithYear,sumNew
    );
    
    cq.groupBy(root.get(Entity1_.dlrCd));

    List<YourPojo> resultado = entityManager.createQuery(cq).getResultList();

您的Pojo必须具有与multiselect方法具有相同参数（顺序和类型）的构造函数。

结果查询：

select
    entity1.DLR_CD as col_0_0_,count(entity1.DLR_CD) as col_1_0_,sum(case when entity1.CMPLT_DT=? then 1 else 0 
        end) as col_2_0_,sum(case when entity1.CMPLT_DT=? then 1  else 0 
        end) as col_3_0_,sum(case when extract(year from entity1.CMPLT_DT)=extract(year from ?)+-1 then 1 else 0 
        end) as col_4_0_,sum(case when extract(year from entity1.CMPLT_DT)=extract(year from ?) then 1 else 0 
        end) as col_5_0_,sum(case when entity1.CMPLT_DT is null or entity1.CMPLT_DT=? then entity1.RPR_LBR_HR else 0 
        end) as col_6_0_,from
    entity1
left join
    entity2 on entity1.PIP_PSP_NO = entity2.PIP_PSP_NO and 
    entity2.ANUN_IND='A'
group by
    entity1.DLR_CD
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