Question

我需要编写查询，但是我不确定如何编写查询。我需要根据状态获取所有EmployeeId。如果已完成且未决，则以完成为准。但是，如果只有待处理的工作尚未完成，我将处理待处理的工作，否则不要处理该员工的任何行。每个EmployeeId我只需要一项。从技术上讲，我也需要最早的时间，但是我想我会写这个部分。

RowNumber  Status    EmployeeId   Produce       Date
-------------------------------------------------------
1          New          1            Apples     1/1/18
2          Pending      1           BlueBerry   1/2/18
3          New          1           Oranges     1/3/18
4          Pending      2            Bananas    1/1/18
5          New          2            Grapes     1/2/18
6          Complete     2            Limes      1/3/18

因此在此示例中，我需要以下内容

RowNumber  Status    EmployeeId    Produce       Date
--------------------------------------------------------
2          Pending      1           BlueBerry   1/2/18
6          Complete     2            Limes      1/3/18

对我来说最困难的部分是试图弄清楚如何比较字符串。基本上（半伪代码）

Select top 1 
    t.EmployeeId, t.Produce, t.Date, stat.Status
    (Case
        If t.Status = 'Complete'
           Select 'Complete'
        If t.Status = 'Pending'
           Select 'Pending'
        Else
           Dont Add this row ) stat
From 
    Table t 
Where 
    t.Status = 'Complete' or t.Status = 'Pending'
Order by 
    t.Date

Answer 1

我想到至少有两种不同的方法：

SELECT DISTINCT EmployeeId
           FROM Table
          WHERE Status = "Complete"

          UNION

SELECT DISTINCT t1.EmployeeId
           FROM Table t1
LEFT OUTER JOIN Table t2
             ON t2.EmployeeId = t1.EmployeeId
            AND t2.Status = "Complete"
          WHERE t1.Status = "Pending"
            AND t2.Status IS NULL

…或如果数据库引擎支持，则使用coalesce()：

SELECT DISTINCT pend.EmployeeId,
                coalesce(comp.Status,pend.Status),
                coalesce(comp.RowNumber,pend.RowNumber)
           FROM MyTable pend
LEFT OUTER JOIN MyTable comp
             ON comp.EmployeeId = pend.EmployeeId
            AND comp.Status = 'Complete'
          WHERE pend.Status IN ('Complete','Pending');

Answer 2

使用row_number()是您想要的吗？

select top (1) with ties *
from table t
where Status in ('Completed', 'Pending')
order by row_number() over (partition by EmployeeId 
                                 order by (case Status when 'Completed' 
                                                       then 0 
                                                       when 'Pending' 
                                                       then 1  
                                           end)
                           );

Answer 3

您可以使用UNION ALL结合WHERE NOT EXISTS来实现：

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Answer 4

您可以计算使用CASE WHEN的ROW_NUMBER。

然后对此进行过滤。

例如：

SELECT RowNumber, [Status], EmployeeId, Produce, [Date]
FROM
(
  SELECT  
   RowNumber, [Status], EmployeeId, Produce, [Date],
   ROW_NUMBER() OVER (
      PARTITION BY EmployeeId 
      ORDER BY [Date] DESC, 
                CASE [Status] WHEN 'Complete' THEN 1 WHEN 'Pending' THEN 2 ELSE 9 END
      ) AS RN
   FROM [YourTable] t 
   WHERE [Status] IN ('Complete','Pending')
) q
WHERE RN = 1
ORDER BY EmployeeId

两行中特定文本的SQL查询条件

4 个答案: