如何根据同一个表中的条件更新表

Question

在上图中，您将注意到前6行显示每个StudentID的2条记录。我需要为每组StudentID更新第二条记录的EndDate列值，其值为ONE DAY，而不是同一StudentID的第一条记录的StatusEffectiveDate。我正在使用SQL Server 2014.

所以第一条记录应该是这样的：

这是我的SQL代码：

py -3.5 -m pip install git+https://github.com/abenassi/Google-Search-API/

任何帮助/指示将不胜感激。

Answer 1

使用ZLK所述的CTE来更新行。

;WITH cte AS
(SELECT 
    * 
  , DATEADD(DAY, -1, LAG(statuseffectivedate) OVER (PARTITION BY StudentID ORDER BY statuseffectivedate DESC)) AS NewDate
FROM #TEMP_99RecordsNeedingEndDateUpdated)

UPDATE cte
SET cte.enddate = cte.NewDate
WHERE cte.NewDate IS NOT NULL

Answer 2

参加晚会，但这里还有一个尝试：

CALCULATE(SUM(TABLE1[FIELD_MEASURE]),DATEADD(TABLE1[DAY_ID].[Date],-1,YEAR))

正如其他人所说，这对您的数据的限制非常有限。

基本上，我是根据来自同一学生ID的MAX（）日期的子查询，将EndDate更新为新值。最后，为了避免更新所有学生记录，我确保StatusEffectiveDate不是更晚的日期。

Answer 3

with cte as 
( select *  
       , row_number over (partition by studentID order by StatusEffectiveDate desc ) as rnD
       , row_number over (partition by studentID order by StatusEffectiveDate asc  ) as rnA
  from table t 
)

select cte.StudentID, cte.Location, cte.Status, cte.EconDisCode, cte.StatusEffectiveDate  
     , cte.EndDate
from cte 
where rnD == 1 
union 
select cteA.StudentID, cteA.Location, cteA.Status, cteA.EconDisCode, cteA.StatusEffectiveDate
     , dateadd(d, -1, cteD.StatusEffectiveDate) 
from cte cteA  
join cte cteD
  on cteA.StudentID = cteD.StudentID 
 and cteA.rnD = 1 
 and cteD.rnA = 1
order by studentID, StatusEffectiveDate desc 


update cteA
set cteA.EndDate = dateadd(d, -1, cteD.StatusEffectiveDate) 
from cte cteA  
join cte cteD
  on cteA.StudentID = cteD.StudentID 
 and cteA.rnD = 1 
 and cteD.rnA = 1
order by studentID, StatusEffectiveDate desc 

包含实际文字（不是图片），因此可以剪切和粘贴

Answer 4

这个限制非常有限，特别是总是需要两行 - 一个＆＃39; Free＆＃39;和一个其他的＆＃39; - 但如果是这种情况，您应该能够进行UNION查询。

  SELECT StudentID, Location, Status, EconDisCode, StatusEffDate, EndDate
  FROM #TEMP_99RecordsNeedingEndDateUpdated 
  WHERE Status = 'Free'
  UNION
  SELECT StudentID, Location, Status, EconDisCode, StatusEffDate, (SELECT StatusEffDate-1 FROM #TEMP_99RecordsNeedingEndDateUpdated t2 WHERE Status = 'Free' AND t1.StudentID = t2.StudentID) AS EndDate
  FROM #TEMP_99RecordsNeedingEndDateUpdated t1 
  WHERE Status = 'Other'

我认为数据的小提琴示例会有所帮助。