如何从访问中的 table 中获取选择性记录

Question

下面是我查询的结果。但是有很多冗余记录，因此，我想过滤掉这个查询的结果。我的目标是每个角度只提取两个记录，第一个和最后一个。例如当角度为195时，我想在 date=2/27/2017，time=2:00:00 AM 和第二条记录，日期为2/27/2017，时间=9:00:00 AM。同样，当角度更改为 210 我想在 date=2/27/2017 time=10:00:00 AM[=28] 时获取其第一条记录=] 和日期和时间为 2/27/2017 和 9:00:00 PM 时的另一条记录。 所有记录也是如此。我试着自己做，但每个角度只有 returns 一条记录，只有最上面的一条，不知道如何获得最后一条。我正在使用两个查询 (Query1)

SELECT final.Date, final.Angle FROM final GROUP BY final.Date, final.Angle

第二个查询是 (fileredOUtput)

SELECT Query1.Date, Query1.Angle, (SELECT TOP 1 final.Date FROM final WHERE Query1.Date=final.Date AND Query1.Angle= final.Angle) AS NewDate, (SELECT TOP 1 final.Angle FROM final WHERE Query1.Date=final.Date AND Query1.Angle= final.Angle) AS NewAngle, (SELECT TOP 1 final.earthCol.Value FROM final WHERE Query1.Date=final.Date AND Query1.Angle= final.Angle) AS NewE_CV, (SELECT TOP 1 final.earthCol.ColNu FROM final WHERE Query1.Date=final.Date AND Query1.Angle= final.Angle) AS New_E_CN, (SELECT TOP 1 final.mars_Col.Value FROM final WHERE Query1.Date=final.Date AND Query1.Angle= final.Angle) AS NewM_CV, (SELECT TOP 1 final.Col_apart FROM final WHERE Query1.Date=final.Date AND Query1.Angle= final.Angle) AS New_CApart, (SELECT TOP 1 final.mars_Col.ColNu FROM final WHERE Query1.Date=final.Date AND Query1.Angle= final.Angle) AS NewM_CN, (SELECT TOP 1 final.Time FROM final WHERE Query1.Date=final.Date AND Query1.Angle= final.Angle) AS NewTime FROM Query1, final WHERE (((Query1.Date) Between [Forms]![Query Form]![txtStartDate] And [Forms]![Query Form]![txtEndDate]));

Query results and results I need are marked with red。期待着听到您的意见。谢谢。

Answer 1

可能是：

SELECT 
    * 
FROM 
    final,

    (SELECT 
        final.Date, Min(final.Time) As MinTime, Max(final.Time) As MaxTime, final.Angle
    FROM 
        final
    GROUP BY 
        final.Date, final.Angle) As T

WHERE
    final.Angle = T.Angle AND
    final.Date = T.Date AND
    ((final.Time = T.MinTime) OR (final.Time = T.MaxTime))
ORDER BY
    final.Date, final.Time, final.Angle

Answer 2

请记住，除非您还 select 来自 table 的时间，否则您无法知道您正在检索哪些值。您所需输出中的日期和角度不是唯一的组合。

您可能需要稍微修改 Access 语法。

SELECT 
    final.Date AS dt, 
    MIN(final.Time) AS tm, 
    final.Angle AS ag
FROM 
    final 
GROUP BY 
    final.Date, final.Angle
UNION SELECT 
    final.Date, 
    MAX(final.Time), 
    final.Angle
FROM 
    final 
GROUP BY 
    final.Date, final.Angle
ORDER BY 
    dt, ag, tm;

编辑：SQL Fiddle 示例... http://sqlfiddle.com/#!9/2f638c/14

Answer 3

试试这个

SELECT * FROM final INNER JOIN
(SELECT Min(DDate + DTime) AS DDateTime, Angle FROM final GROUP BY Angle
UNION SELECT Max(DDate + DTime) AS DDateTime, Angle FROM final GROUP BY Angle) mm
ON final.DDate + final.DTime = mm.DDateTime AND final.Angle = mm.Angle

请注意，在测试中我将前两列的名称分别更改为DDate和DTime，因为Date和Time是保留字。

编辑

这使得它变得相当困难，特别是在没有 LEAD/LAG 功能的 Access 中。以下应该可行，但有人可能有更优雅的解决方案！

SELECT final.* FROM final INNER JOIN
(SELECT MIN(DDateTime) AS MDateTime, Angle FROM
(SELECT (f.DDate+ f.DTime) AS DDateTime, f.Earth_Value, f.Mars_Value, f.Earth_Col, f.Mars_Col, f.Diff, f.Angle, f.Col_Apart,
IIF(ISNULL((SELECT MIN(m.DDate + m.DTime) FROM final m where f.angle <> m.angle and (f.DDate+f.DTime) < (m.DDate+m.DTime))),
(SELECT MAX(DDate+DTime) FROM final),(SELECT MIN(m.DDate + m.DTime) FROM final m where f.angle <> m.angle and (f.DDate+f.DTime) < (m.DDate+m.DTime))) AS NextChangeDateTime
FROM final f order by DDate, DTime) g
GROUP BY g.Angle,g.NextChangeDateTime
UNION
SELECT MAX(DDateTime) AS MDateTime, Angle FROM
(SELECT (f.DDate+ f.DTime) AS DDateTime, f.Earth_Value, f.Mars_Value, f.Earth_Col, f.Mars_Col, f.Diff, f.Angle, f.Col_Apart,
IIF(ISNULL((SELECT MIN(m.DDate + m.DTime) FROM final m where f.angle <> m.angle and (f.DDate+f.DTime) < (m.DDate+m.DTime))),
(SELECT MAX(DDate+DTime) FROM final),(SELECT MIN(m.DDate + m.DTime) FROM final m where f.angle <> m.angle and (f.DDate+f.DTime) < (m.DDate+m.DTime))) AS NextChangeDateTime
FROM final f order by DDate, DTime) g
GROUP BY g.Angle,g.NextChangeDateTime) FLDates
ON final.DDate + final.DTime = FLDates.MDateTime

编辑 2

从技术上讲，MS Access 中没有临时 table 这样的东西。实际上，您只需创建一个普通的 table 并在每次要使用它时删除其内容。

要创建 table，您需要将其复制到查询 Window（SQL 视图），然后单击运行:

CREATE TABLE final (
    DDate       DATETIME     NOT NULL,
    DTime       DATETIME     NOT NULL,
    Earth_Value         DOUBLE   NOT NULL,
    Mars_Value         DOUBLE   NOT NULL,
    Earth_Col           INTEGER     NOT NULL,
    Mars_Col           INTEGER     NOT NULL,
    Diff           INTEGER     NOT NULL);

然后在你现有的查询类型之前（你只需要第一行）：

INSERT into final
SELECT etc.

现在您将能够运行我的查询完全按原样进行。

如何从访问中的 table 中获取选择性记录

How can I get selective records from a table in access

sql

database

ms-access

ms-access-2013