查询具有两个 ID 字段的 Table

Question

我有一个名为 Actions 的 table，有 2 个标识符：Ref 和 Status
状态可以是以下任何一种：new、done

  Ref  |  Status  |  Date   
  ---------------------------------- 
   1   |   new    | 10/31/2018   
   1   |   done   | 10/31/2018
   2   |   new    | 10/31/2018

我只想查询 new 而不是 done 的操作。在此示例中，查询将仅 return table.

的第 3 行

到目前为止，这是我尝试过的方法，但我只获得了已置于状态的操作 done:

SELECT [2].[project title], [2].ref, [2].[Date] As [Creation Date]
    FROM (SELECT * From T_ACTIONS Where status = "New") AS [1],  
         (SELECT * From T_ACTIONS Where status = "Done") AS [2]
    WHERE [1].[Project Title] = [Insert a valid : Project Title]
    AND [1].[REF] = [2].[Ref]

我使用的是 Access 2016。

Answer 1

使用NOT EXISTS：

SELECT a.*
FROM Actions a
WHERE Status = 'new' AND
      NOT EXISTS (SELECT 1 FROM Actions a1 WHERE a1.REF = a.REF AND a1.Status = 'Done');

Answer 2

您可以 LEFT JOIN 您的操作 table 到嵌套 SELECT 查询检索状态为 Done 的所有引用，并测试在嵌套查询，例如：

SELECT a.*
FROM 
    Actions a LEFT JOIN (SELECT b.Ref FROM Actions b WHERE b.Status = 'Done') t
    ON a.Ref = t.Ref
WHERE
    a.Status = 'New' AND t.Ref IS NULL

Answer 3

另一种方法使用聚合：

select ref
from actions
where status in ('new', 'done')
group by ref
having min(status) = max(status) and min(status) = 'new';

查询具有两个 ID 字段的 Table

Querying a Table with two ID Fields

sql

ms-access

ms-access-2016