如何使用SQL从日期范围内的特定小时开始按天计数记录

Question

我有一个datetime字段，我想按日期计算从8:00到9:00的一天中的日期范围内的所有记录（即：从：01/01/2012到：01/03/2012）。

例如，如果我有以下数据：

2012-01-01 08:26
2012-01-01 08:40
2012-01-01 09:26
2012-01-01 10:26
2012-01-02 08:06
2012-01-02 09:26
2012-01-02 09:40
2012-01-03 08:30
2012-01-03 10:26

结果应如下所示：

2012-01-01 2
2012-01-02 1
2012-01-03 1

编辑：这是我使用@gbn解决方案得到的（对我有用）

SELECT    COUNT(*),  convert(varchar(10),ScanDate,101)
FROM    tblSingleBox (nolock)
WHERE    DATEPART(Hour, scandate) = 8
    and (scandate>='01/03/2012' and scandate<'01/05/2012')
GROUP BY    convert(varchar(10),ScanDate,101) 
order by convert(varchar(10),ScanDate,101)

Answer 1

SQL Server 2005及更早版本

SELECT
   COUNT(*),
   DATEADD(dd, DATEDIFF(dd, 0, SomeDateTime), 0)
   -- SQL Server 2008: CAST(SomeDateTime AS date)
FROM
   SomeTable
WHERE
   DATEPART(Hour, SomeDateTime) = 8
GROUP BY
   DATEADD(dd, DATEDIFF(dd, 0, SomeDateTime), 0);
   -- SQL Server 2008: CAST(SomeDateTime AS date);

MySQL：

SELECT
   COUNT(*),
   DATE(SomeDateTime)
FROM
   SomeTable
WHERE
   HOUR(SomeDateTime) = 8
GROUP BY
   DATE(SomeDateTime);

Answer 2

在这种情况下，最简单的代码和最快的代码可能会相差很大，并且可能取决于数据集的大小。

我怀疑最快的方法是加入日历和过滤器。 在这种情况下，我会在开始之前制作一个日历，但我建议您使用一个永久的日历...

CREATE TABLE #calendar (
  date AS DATETIME
)
INSERT INTO #calendar SELECT '2011-12-31' UNION ALL SELECT '2012-01-01'
            UNION ALL SELECT '2012-01-02' UNION ALL SELECT '2012-01-03'
            UNION ALL SELECT '2012-01-04' UNION ALL SELECT '2012-01-05'

SELECT
  calendar.date,
  COUNT(*)
FROM
  yourTable
INNER JOIN
  #calendar    AS calendar
    ON  yourTable.DateTimeField >= calendar.date + @minTime
    AND yourTable.DateTimeField <  calendar.date + @maxTime
WHERE
      calendar.date >= @startDate
  AND calendar.date <= @endDate
GROUP BY
  calendar.date

这应该产生对索引最友好的查询，因此对于任何合理大小的数据而言，它都是非常有效的。

注意：

calendar.date + @Time部分将有所不同。 您刚刚说过MS SQL Server，所以它更像是...

    ON  yourTable.DateTimeField >= DATEADD(hour, @minHour, calendar.date)
    AND yourTable.DateTimeField <  DATEADD(hour, @maxHour, calendar.date)

Answer 3

SQL Server 2005

IF OBJECT_ID('tempdb.dbo.#DATES') IS NOT NULL
    DROP TABLE #DATES

CREATE TABLE #DATES
    (   LogDate smalldatetime   )

INSERT INTO #DATES
    (   LogDate )
            SELECT  '2012-01-01 08:26'
UNION SELECT '2012-01-01 08:40'
UNION SELECT '2012-01-01 09:26'
UNION SELECT '2012-01-01 10:26'
UNION SELECT '2012-01-02 08:06'
UNION SELECT '2012-01-02 09:26'
UNION SELECT '2012-01-02 09:40'
UNION SELECT '2012-01-03 08:30'
UNION SELECT '2012-01-03 10:26'
UNION SELECT '2012-01-03 15:26'

DECLARE @nStartHour smallint
DECLARE @nEndHour smallint

SET @nStartHour = 15
SET @nEndHour = 16

SELECT  CONVERT(varchar, LogDate, 101), COUNT(*)
FROM        #DATES
WHERE       DATEPART(hour,LogDate) BETWEEN @nStartHour AND (@nEndHour - 1)
GROUP BY CONVERT(varchar, LogDate, 101)