Question

我试图根据其中一列的最大日期撤回一行详细信息。做一个简单的max（date.field）对我的表不起作用。我最初通过利用我使用此资源构建的查询来解决了这个问题See the entry by Tom H.：

SELECT
    HBM_CLIENT.CLIENT_CODE,
    HBM_NAME.NAME AS CLIENT_NAME,
    PART_BILL1.PART_CAT_CODE AS BILLING_CODE,
    PART_BILL1.EMPL_UNO AS BILLING_NAME_UNO,
    HBM_PERSNL_BILL.EMPLOYEE_NAME AS BILLING_NAME,
    PART_BILL1.PERCENTAGE AS BILLING_PERCENTAGE
FROM 
    HBM_CLIENT
INNER JOIN 
    HBM_NAME ON HBM_CLIENT.NAME_UNO = HBM_NAME.NAME_UNO
LEFT OUTER JOIN 
    TBM_CLMAT_PART AS PART_BILL1 ON PART_BILL1.CLIENT_UNO = HBM_CLIENT.CLIENT_UNO
                                 AND PART_BILL1.PART_CAT_CODE = 'BILL'
LEFT OUTER JOIN 
    TBM_CLMAT_PART AS PART_BILL2 ON PART_BILL2.CLIENT_UNO = HBM_CLIENT.CLIENT_UNO
                                 AND PART_BILL2.EFF_DATE > PART_BILL1.EFF_DATE
                                 AND PART_BILL1.PART_CAT_CODE = 'BILL'
LEFT OUTER JOIN 
    HBM_PERSNL AS HBM_PERSNL_BILL ON PART_BILL1.EMPL_UNO = HBM_PERSNL_BILL.EMPL_UNO
GROUP BY 
    HBM_CLIENT.CLIENT_CODE, HBM_NAME.NAME,
    PART_BILL1.PART_CAT_CODE, PART_BILL1.EMPL_UNO,
    HBM_PERSNL_BILL.EMPLOYEE_NAME,
    PART_BILL1.PERCENTAGE,
ORDER BY 
    HBM_CLIENT.CLIENT_CODE

此查询的问题在于，由于某种原因，它不会撤回所有结果，原因在于我使用的解决方案。

我想知道使用case语句是否更有意义，但我对case语句不是很熟悉。

以下是我正在处理的查询：

`SELECT
  HBM_CLIENT.CLIENT_CODE,
  HBM_NAME.NAME AS CLIENT_NAME,
  PART_BILL1.PART_CAT_CODE AS BILLING_CODE,
  PART_BILL1.EMPL_UNO AS BILLING_NAME_UNO,
  HBM_PERSNL_BILL.EMPLOYEE_NAME AS BILLING_NAME,
  PART_BILL1.PERCENTAGE AS BILLING_PERCENTAGE,
  Part_BILL1.EFF_DATE,
 CASE
    WHEN 
    MAX(Part_BILL1.EFF_DATE) > Part_BILL1.EFF_DATE THEN max(Part_BILL1.EFF_DATE) ELSE Part_BILL1.EFF_DATE END  
FROM HBM_CLIENT
INNER JOIN HBM_MATTER
  ON HBM_CLIENT.CLIENT_UNO = HBM_MATTER.CLIENT_UNO
INNER JOIN HBM_NAME
  ON HBM_CLIENT.NAME_UNO = HBM_NAME.NAME_UNO
LEFT OUTER JOIN TBM_CLMAT_PART AS PART_BILL1
  ON PART_BILL1.CLIENT_UNO = HBM_CLIENT.CLIENT_UNO
  AND PART_BILL1.PART_CAT_CODE = 'BILL'
LEFT OUTER JOIN HBM_PERSNL AS HBM_PERSNL_BILL
  ON PART_BILL1.EMPL_UNO = HBM_PERSNL_BILL.EMPL_UNO
WHERE 
(HBM_CLIENT.CLIENT_CODE = '065011') 
GROUP BY
  HBM_CLIENT.CLIENT_CODE,
  HBM_NAME.NAME,
  PART_BILL1.PART_CAT_CODE,
  PART_BILL1.EMPL_UNO,
  HBM_PERSNL_BILL.EMPLOYEE_NAME,
  PART_BILL1.PERCENTAGE,
  Part_BILL1.EFF_DATE
HAVING 
(Part_BILL1.EFF_DATE = CASE
WHEN MAX(Part_BILL1.EFF_DATE) > Part_BILL1.EFF_DATE THEN max(Part_BILL1.EFF_DATE) ELSE Part_BILL1.EFF_DATE END)`

它会运行，但它会让我返回两行而不是一行，即它不会拉动最大值。我正在使用T-SQL并使用Visual Studio编写SSRS。

我很乐意回答任何问题。如果我的解释不是很好，我会提前道歉。

| CLIENT_CODE | CLIENT_NAME  | BILLING_NAME | EFF_DATE | PERCENTAGE |
| ------------+--------------+--------------+----------+------------|
| 123456      | Entity, Inc. | Attorney A   | 1/1/1990 |50%         |
| 123456      | Entity, Inc. | Attorney B   | 1/1/1990 |50%         |
| 123456      | Entity, Inc. | Attorney B   | 1/1/2017 |50%         |
| 123456      | Entity, Inc. | Attorney C   | 1/1/2017 |50%         |

Answer 1

使用带有SELECT TOP 1子句的ORDER BY查询是否可以简化这一点？

这样的事情：

SELECT TOP 1
  HBM_CLIENT.CLIENT_CODE,
  HBM_NAME.NAME AS CLIENT_NAME,
  PART_BILL1.PART_CAT_CODE AS BILLING_CODE,
  PART_BILL1.EMPL_UNO AS BILLING_NAME_UNO,
  HBM_PERSNL_BILL.EMPLOYEE_NAME AS BILLING_NAME,
  PART_BILL1.PERCENTAGE AS BILLING_PERCENTAGE,
  Part_BILL1.EFF_DATE,
  ....
FROM HBM_CLIENT
INNER JOIN HBM_MATTER
  ON HBM_CLIENT.CLIENT_UNO = HBM_MATTER.CLIENT_UNO
INNER JOIN HBM_NAME
  ON HBM_CLIENT.NAME_UNO = HBM_NAME.NAME_UNO
LEFT OUTER JOIN TBM_CLMAT_PART AS PART_BILL1
  ON PART_BILL1.CLIENT_UNO = HBM_CLIENT.CLIENT_UNO
  AND PART_BILL1.PART_CAT_CODE = 'BILL'
LEFT OUTER JOIN HBM_PERSNL AS HBM_PERSNL_BILL
  ON PART_BILL1.EMPL_UNO = HBM_PERSNL_BILL.EMPL_UNO
WHERE 
(HBM_CLIENT.CLIENT_CODE = '065011') 
ORDER BY Part_BILL1.EFF_DATE DESC

这应该只给你EFF_DATE的最新行，而不需要任何特殊的分组或案例逻辑。

编辑：在我看来，获得所需结果的最佳方法是利用TOP子句。通常，在编写查询时   像这样，你会写SELECT TOP 1或SELECT TOP 1000，但是   TOP子句也支持各种功能。您可以使用   子查询，计算，变量以及WITH TIES   获得你想要的功能。

在您的情况下，您希望查询返回任意数量的行，这么长   因为它们都具有相同的EFF_DATE值，这也是。{   表格中给定EFF_DATE的最大CLIENT_CODE值。

因此，我建议只添加WITH TIES参数   TOP子句用于获取您正在寻找的功能：
SELECT TOP 1 WITH TIES
  HBM_CLIENT.CLIENT_CODE,
  HBM_NAME.NAME AS CLIENT_NAME,
  PART_BILL1.PART_CAT_CODE AS BILLING_CODE,
  PART_BILL1.EMPL_UNO AS BILLING_NAME_UNO,
  HBM_PERSNL_BILL.EMPLOYEE_NAME AS BILLING_NAME,
  PART_BILL1.PERCENTAGE AS BILLING_PERCENTAGE,
  Part_BILL1.EFF_DATE,
  ....
FROM HBM_CLIENT
INNER JOIN HBM_MATTER
  ON HBM_CLIENT.CLIENT_UNO = HBM_MATTER.CLIENT_UNO
INNER JOIN HBM_NAME
  ON HBM_CLIENT.NAME_UNO = HBM_NAME.NAME_UNO
LEFT OUTER JOIN TBM_CLMAT_PART AS PART_BILL1
  ON PART_BILL1.CLIENT_UNO = HBM_CLIENT.CLIENT_UNO
  AND PART_BILL1.PART_CAT_CODE = 'BILL'
LEFT OUTER JOIN HBM_PERSNL AS HBM_PERSNL_BILL
  ON PART_BILL1.EMPL_UNO = HBM_PERSNL_BILL.EMPL_UNO
WHERE 
(HBM_CLIENT.CLIENT_CODE = '065011') 
ORDER BY Part_BILL1.EFF_DATE DESC
TOP子句的各种用法的完整解释可以是   找到here.

简要解释一下，WITH TIES参数意味着你想要的   查询以基于值返回数据集的TOP X行   在ORDER BY子句中 - 在您的情况下，EFF_DATE。所以，如果有的话   两行EFF_DATE中具有相同值，或三行或五行   一百，他们都会被归还，因为你是有效的   搜索不是TOP 1 ROW，而是搜索   TOP 1 VALUE of EFF_DATE

希望有所帮助。

最大日期/案例陈述

1 个答案: