如何使用逻辑条件在现有表上创建查询并使用布尔数据构建表（视图）？

Question

我拥有的是一个 MS-SQL 数据库，用于存储来自某些车辆上安装的设备的数据/信息（每辆车 1-3 个设备）。

目前，数据库中有一个名为Communication 的表——一个大表，用于存储设备连接到 TCP 服务器时的所有信息。记录一个接一个地添加（这里只插入）。

表格如下所示：

我需要的是一个SQL 查询（命令/语句）来为所谓的“每周通信状态”创建一个表（视图），在那里我可以看到 车辆是否/如何进行通信过去 7 天...类似于下表：

Answer 1

作为上述的替代方案，假设您知道输出中只有 7 个日期列，您可以进行手动透视而不是使用 PIVOT 运算符。

See SQLFiddle

select VehicleNumber, 
      CASE WHEN SUM(CASE WHEN DATEDIFF(d,DateTimeCommunication, DATEADD(d,-7,GETDATE())) = 0 THEN 1 ELSE 0 END) > 0 THEN 'YES' Else 'NO' END AS [7 Days Ago]
      ,CASE WHEN SUM(CASE WHEN DATEDIFF(d,DateTimeCommunication, DATEADD(d,-6,GETDATE())) = 0 THEN 1 ELSE 0 END) > 0 THEN 'YES' Else 'NO' END AS [6 Days Ago]
      ,CASE WHEN SUM(CASE WHEN DATEDIFF(d,DateTimeCommunication, DATEADD(d,-5,GETDATE())) = 0 THEN 1 ELSE 0 END) > 0 THEN 'YES' Else 'NO' END AS [5 Days Ago]
      ,CASE WHEN SUM(CASE WHEN DATEDIFF(d,DateTimeCommunication, DATEADD(d,-4,GETDATE())) = 0 THEN 1 ELSE 0 END) > 0 THEN 'YES' Else 'NO' END AS [4 Days Ago]
      ,CASE WHEN SUM(CASE WHEN DATEDIFF(d,DateTimeCommunication, DATEADD(d,-3,GETDATE())) = 0 THEN 1 ELSE 0 END) > 0 THEN 'YES' Else 'NO' END AS [3 Days Ago]
      ,CASE WHEN SUM(CASE WHEN DATEDIFF(d,DateTimeCommunication, DATEADD(d,-2,GETDATE())) = 0 THEN 1 ELSE 0 END) > 0 THEN 'YES' Else 'NO' END AS [2 Days Ago]
      ,CASE WHEN SUM(CASE WHEN DATEDIFF(d,DateTimeCommunication, DATEADD(d,-1,GETDATE())) = 0 THEN 1 ELSE 0 END) > 0 THEN 'YES' Else 'NO' END AS [1 Days Ago]
      ,CASE WHEN SUM(CASE WHEN DATEDIFF(d,DateTimeCommunication, GETDATE()) = 0 THEN 1 ELSE 0 END) > 0 THEN 'YES' Else 'NO' END AS [0 Days Ago]
from Communications
GROUP BY VehicleNumber

Answer 2

这是一个动态的PIVOT 方法。

CREATE TABLE #temp(equipmentID int, vehicleNumber int, DateTimeCommunication datetime)

INSERT INTO #temp(equipmentID, vehicleNumber, DateTimeCommunication)
VALUES  (1,100,GETDATE()),
        (2,110,GETDATE()),
        (3,120,GETDATE()),
        (5,140,GETDATE()),
        (1,100,DATEADD(day,-8,GETDATE())),
        (3,120,DATEADD(day,-8,GETDATE())),
        (4,130,DATEADD(day,-8,GETDATE())),
        (5,140,DATEADD(day,-8,GETDATE()))

DECLARE @sql nvarchar(max), @columns nvarchar(max), @columnsSelect nvarchar(max)

SELECT @columns = COALESCE(@columns + N',['+CONVERT(nvarchar(max),dateCom)+N']',N'['+CONVERT(nvarchar(max),dateCom)+N']')
FROM (
    SELECT DISTINCT CONVERT(date, DateTimeCommunication) as dateCom
    FROM #temp
) as allDates
ORDER BY dateCom

SELECT @columnsSelect = COALESCE(@columnsSelect + N',ISNULL(['+CONVERT(nvarchar(max),dateCom)+N'],N''NO'') as '''+CONVERT(nvarchar(max),dateCom)+'''',
                                    N'ISNULL(['+CONVERT(nvarchar(max),dateCom)+N'],N''NO'') as '''+CONVERT(nvarchar(max),dateCom)+'''')
FROM (
    SELECT DISTINCT CONVERT(date, DateTimeCommunication) as dateCom
    FROM #temp
) as allDates
ORDER BY dateCom

SET @sql = N'SELECT pvt.vehicleNumber, '+@columnsSelect+'
FROM (
    SELECT t.equipmentID, t.vehicleNumber, CONVERT(date,DateTimeCommunication) as dateCom,
        CASE WHEN t.DateTimeCommunication BETWEEN DATEADD(day,-7,GETDATE()) AND GETDATE() 
            THEN N''YES''
            ELSE N''NO''
        END as communicated
    FROM #temp t
) as dat
PIVOT(
    MAX(communicated)
    FOR dateCom IN('+@columns+')
) as pvt'
PRINT(@sql)
EXEC (@sql)

DROP TABLE #temp

如果您不需要它是动态的或仅用于指定的日期范围，只需将其再次简化为：

CREATE TABLE #temp(equipmentID int, vehicleNumber int, DateTimeCommunication datetime)

INSERT INTO #temp(equipmentID, vehicleNumber, DateTimeCommunication)
VALUES  (1,100,GETDATE()),
        (2,110,GETDATE()),
        (3,120,GETDATE()),
        (5,140,GETDATE()),
        (1,100,DATEADD(day,-8,GETDATE())),
        (3,120,DATEADD(day,-8,GETDATE())),
        (4,130,DATEADD(day,-8,GETDATE())),
        (5,140,DATEADD(day,-8,GETDATE()))

SELECT *
FROM (
    SELECT t.equipmentID, t.vehicleNumber, CONVERT(date,DateTimeCommunication) as dateCom,
        CASE WHEN t.DateTimeCommunication BETWEEN DATEADD(day,-7,GETDATE()) AND GETDATE() 
            THEN N'YES'
            ELSE N'NO'
        END as communicated
    FROM #temp t
) as dat
PIVOT(
    MAX(communicated)
    FOR dateCom IN([2015-06-23]) --needs to be changed on different date!
) as pvt

DROP TABLE #temp