我需要将一些日期间隔除以分钟。(例如,2012-01-01 10:00 - 2012-01-01 10:00 间隔应分为 2012-01-01 10:01、2012-01-01 10:02、... 2012-01 -01 10:10)。例如,有一张桌子
CREATE TABLE [dbo].[Events](
[ID] [int] IDENTITY(1,1) NOT NULL,
[EventStart] [datetime] NOT NULL,
[EventEnd] [datetime] NOT NULL,
[Amount] [float] NOT NULL,
CONSTRAINT [PK_Events] PRIMARY KEY CLUSTERED
(
[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
这张桌子被填满了
DECLARE @i integer = 0;
DECLARE @initial_date datetime = '2012-01-01';
WHILE @i < 50000
BEGIN
INSERT INTO [Events] (EventStart, EventEnd, Amount) VALUES (DATEADD(MINUTE, 10*@i, @initial_date), DATEADD(MINUTE, 10*(@i + 1), @initial_date), @i);
SET @i = @i + 1;
END
因此,我们有许多 10 分钟的间隔。
要将其除以分钟,我使用以下递归 CTE:
DECLARE @start_date datetime = '2012-01-01';
DECLARE @end_date datetime = '2013-01-02';
WITH Date_Ranges (StatDate, Amount, IntervalStart, CurrentMinute) AS (
SELECT
DATEADD(MINUTE, 0, ev.EventStart) AS StatDate, ev.Amount, ev.EventStart AS IntervalStart, 1 AS CurrentMinute
FROM [Events] ev
WHERE ev.EventStart BETWEEN @start_date AND @end_date
UNION ALL
SELECT
DATEADD(MINUTE, CurrentMinute, ev.EventStart), ev.Amount, ev.EventStart AS IntervalStart, CurrentMinute + 1
FROM [Events] ev
INNER JOIN Date_Ranges ranges ON (ranges.IntervalStart = ev.EventStart AND
ranges.StatDate >= ev.EventStart AND
ranges.StatDate < ev.EventEnd)
WHERE DATEADD(MINUTE, CurrentMinute, ev.EventStart) BETWEEN @start_date AND @end_date AND
ev.EventStart BETWEEN @start_date AND @end_date
)
SELECT *
FROM Date_Ranges --ORDER BY StatDate
主要问题是在大量数据上执行此递归 CTE 太慢。
那么,我怎样才能加快速度呢?