Question

我正在尝试规范化工作数据库，目前其中一个表大约有120列，我正在构建一个新表来纠正许多问题。

我正在试图弄清楚如何编写查询，找出哪些Panel仍然安装。

表中的字段中，一些最相关的是：

ActualCompleteDate
PanelID 
WorkType ("electrical install", "electrical removal")

我需要编写一个可以隔离所有已安装Panel的查询，并允许我获取其ID，以便我可以使用该查询将所有必要的数据迁移到新表。还有12个其他列需要移动到新表中。

修改

完整的查询基于下面的FuzzyTree解决方案：

SELECT  CHSRNumber,CableSize,CableLength,[CEA Type],CHSRLoc
        ,PanelID,ConnectorType,BreakerAmps,Voltage,[Status]
        ,InstallRDCLoc,Phase,UPS,BreakerType,ActualCompleteDate 
FROM (
    SELECT  CHSRNumber,CableSize,CableLength,[CEA Type],CHSRLoc
            ,PanelID,ConnectorType,BreakerAmps,Voltage,[Status]
            ,InstallRDCLoc,Phase,UPS,BreakerType,WorkType,[ActualCompleteDate]
            ,row_number() OVER (
                PARTITION BY PanelID 
                ORDER BY ActualCompleteDate DESC
            ) rn 
    FROM    [Facilities_Database].[Facilities].[HardwareSupportRequest] t1
) t1 
WHERE rn = 1 AND [WorkType] LIKE '%electric install%' 
    --AND (CableLength IS NOT NULL
    --  OR [CEA Type] IS NOT NULL 
    --  OR [CableSize] IS NOT NULL)
ORDER BY CHSRNumber

Answer 1

这将选择已安装但尚未在安装后删除的所有PanelID

select PanelID from (
    select PanelID,
    row_number() over (partition by PanelID order by ActualCompleteDate desc) rn,
    WorkType
    from mytable
) t1 where rn = 1 and WorkType = "electrical install"

如果您的数据库不支持row_number（）

，则

或使用不存在

select PanelID from mytable t1
where WorkType = "electrical install"
and not exists (
    select 1 from mytable t2
    where t2.PanelID = t1.PanelID
    and t2.ActualCompleteDate > t1.ActualCompleteDate
    and t2.WorkType = "electrical removal"
)

Answer 2

另一种方法，更容易调试/扩展：

select i.* from
(select
 PanelID, 
 max(ActualCompleteDate) as max_datei
from 
 table
where
 worktype = "electrical install"
group by
 PanelID) i left outer join
(select
 PanelID, 
 max(ActualCompleteDate) as max_dater 
from 
 table
where
 worktype = "electrical removal"
group by
 PanelID) r on 
i.panelid = r.panelid and
maxdatei > maxdater or 
maxdater is null

确定对每个项目执行的最后一个操作是安装还是删除

2 个答案: