Question

我在SQL Server 2012中有一个包含天气数据（每隔2分钟）的表

 CREATE TABLE [dbo].[Test]
 (
     [SampleDateTime] [datetime] NULL,
     [Unit ID] [nvarchar](4) NULL,
     [WS Avg 2min] [float] NULL,
     [WD Avg 2min] [float] NULL,
     [WGS 10min] [float] NULL,
     [WGD 10min] [float] NULL,
     [Air Temp] [float] NULL,
     [Rel Humidity] [float] NULL,
     [Dew Point] [float] NULL,
     [Pyranometer] [float] NULL,
     [Quantum] [float] NULL,
     [Air Pressure] [float] NULL,
     [Snow Level] [float] NULL,
     [Rainfall] [float] NULL,
     [PW Current] [varchar](10) NULL,
     [Visibility] [float] NULL,
     [CBase 1] [float] NULL,
     [CBase 2] [float] NULL,
     [CBase 3] [float] NULL,
     [Vert Vis] [float] NULL
 ) ON [PRIMARY]

我试图在一个月内获得每天的盛行风向。所以基本上是每天的方向计数，返回最大计数。有了这个查询，我就接近了（来自MS Access）

SELECT 
    Day([SampleDateTime]) AS [Date], 
    Round([WD Avg 2min],0) AS  WindDir,
    Count(Round([WD Avg 2min],0)) AS [Count]
FROM 
    WeatherData
WHERE 
    (((Year([SampleDateTime]) * 12 + DatePart("m", [SampleDateTime])) = Year(Date()) * 12 + DatePart("m", Date()) - 0))
GROUP BY 
    Day([SampleDateTime]), Round([WD Avg 2min],0)
ORDER BY 
    Day([SampleDateTime]), Count(Round([WD Avg 2min],0)) DESC;

我得到了这个结果

Date   WindDir  Count
1      74       45
1      342      11
1      331      11
1      333      11
1      338      10
2      48       20
2      45       20
2      42       20
2      50       17

我似乎无法让查询返回相同的结果，但每个日期只有Max“Count”，如下所示

Date   WindDir  Count
1      74       45
2      48       20

么？

Answer 1

我猜你的第一个查询是正确的，并希望减少到第二个结果。

使用CTE Using Common Table Expressions

SQL FIDDLE

test = serializers.CharField(required=False, read_only=True)

SQL查询按日期选择盛行风向

1 个答案: