How to Create Times Based on an Interval and Start Time? - sql

Question

I am performing some scheduling optimization in my database.
For the job schedule, many records appear like this
Time NextRunTime
Every 3 hours 2019-06-03 10:00:00
Every 3 hours 2019-05-28 20:00:00
Every 4 hours 2017-07-31 18:00:00
Every 1 hours 2019-06-03 14:00:00
Every 4 hours 2017-06-08 16:00:00
What is an efficient means to split the "every" records into separate records within the 24 hour day?
For example, for the first record (every 3 hours from 10:00), I need it to insert the following into a table.
Time
13:00:00
16:00:00
19:00:00
22:00:00
01:00:00
04:00:00
07:00:00
10:00:00
I need to repeat this for every record in the first table with "every".
Can anybody help?

Answer 1

If you want to do this correctly you will need a tally table. First let's look at the logic required to solve this.
DECLARE #starttime DATETIME = '2019-06-03 10:00:00', #hours INT = 3;
SELECT t.N, Tm = CAST(DATEADD(HOUR,t.N*3,#startTime) AS TIME)
FROM
(
SELECT TOP (24/#hours) ROW_NUMBER() OVER (ORDER BY (SELECT 1))
FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) AS a(x),
(VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) AS b(x)
) AS t(N);
Returns:
N Tm
------- ----------------
1 13:00:00.0000000
2 16:00:00.0000000
3 19:00:00.0000000
4 22:00:00.0000000
5 01:00:00.0000000
6 04:00:00.0000000
7 07:00:00.0000000
8 10:00:00.0000000
Now for some sample data and a record identifier (named "someId") so we can calculate this for all rows in your table.
-- Sample Data
DECLARE #yourTable TABLE (someId INT IDENTITY PRIMARY KEY, freq INT, NextRunTime DATETIME);
INSERT #yourTable(freq, NextRunTime) VALUES (3, '2019-06-03 10:00:00'),
(3, '2019-05-28 20:00:00'),(4, '2017-07-31 18:00:00'),
(1, '2019-06-03 14:00:00'),(4, '2017-06-08 16:00:00');
-- Solution
SELECT yt.someId, f.Tm
FROM #yourTable AS yt
CROSS APPLY
(
SELECT t.N, CAST(DATEADD(HOUR,t.N*yt.freq,yt.NextRunTime) AS TIME)
FROM
(
SELECT TOP (24/yt.freq) ROW_NUMBER() OVER (ORDER BY (SELECT 1))
FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) AS a(x),
(VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) AS b(x)
) AS t(N)
) AS f(N,Tm);
Returns:
someId Tm
----------- ----------------
1 13:00:00.0000000
1 16:00:00.0000000
1 19:00:00.0000000
1 22:00:00.0000000
1 01:00:00.0000000
1 04:00:00.0000000
1 07:00:00.0000000
1 10:00:00.0000000
2 23:00:00.0000000
2 02:00:00.0000000
2 05:00:00.0000000
2 08:00:00.0000000
2 11:00:00.0000000
2 14:00:00.0000000
2 17:00:00.0000000
2 20:00:00.0000000
3 22:00:00.0000000
3 02:00:00.0000000
3 06:00:00.0000000
3 10:00:00.0000000
3 14:00:00.0000000
3 18:00:00.0000000
4 15:00:00.0000000
4 16:00:00.0000000
4 17:00:00.0000000
4 18:00:00.0000000
4 19:00:00.0000000
4 20:00:00.0000000
4 21:00:00.0000000
4 22:00:00.0000000
4 23:00:00.0000000
4 00:00:00.0000000
4 01:00:00.0000000
4 02:00:00.0000000
4 03:00:00.0000000
4 04:00:00.0000000
4 05:00:00.0000000
4 06:00:00.0000000
4 07:00:00.0000000
4 08:00:00.0000000
4 09:00:00.0000000
4 10:00:00.0000000
4 11:00:00.0000000
4 12:00:00.0000000
4 13:00:00.0000000
4 14:00:00.0000000
5 20:00:00.0000000
5 00:00:00.0000000
5 04:00:00.0000000
5 08:00:00.0000000
5 12:00:00.0000000
5 16:00:00.0000000

Answer 2

I have always thought that a recursive cte is a nice way to solve your query:
-- the sample data
declare #data as table (freq varchar(100), tmst datetime, each_ int)
insert into #data
select s.freq,s.tmst,
convert(int,replace(replace(freq,'Every ',''),' hours','')) as each_
from (
select 'Every 4 hours' as freq, convert(datetime,'2019-06-02 10:00:00') as tmst union all
select 'Every 3 hours' as freq, convert(datetime,'2019-06-02 11:00:00') as tmst union all
select 'Every 2 hours' as freq, convert(datetime,'2019-06-02 10:00:00') as tmst
) s
-- the query
;with cte as (
select freq, tmst, each_, null t1 from #data
union all
select freq, tmst, each_, isnull(t1,datepart(hour,tmst)) + each_
from cte
where isnull(t1,datepart(hour,tmst)) + each_ <= 23
)
select freq,
isnull(convert(datetime, convert(varchar(8),tmst,112) + ' ' + (convert(varchar(100),t1) + ':00:00' ), 120),tmst)
from cte
order by 1, 2
With this second version, you can get all the ranges from 0 to 23 (in the previous example you got just from the starting point to the 23)
-- the query
;with findfirst as (
select freq, tmst, datepart(hour,tmst) as fhour, datepart(hour,tmst) as init, each_ from #data
union all
select freq, tmst, fhour, init - each_, each_ from findfirst where init - each_ >= 0
),
cte as (
select min(init) as init, freq, tmst, each_, fhour from findfirst group by freq, tmst, each_, fhour
union all
select init + each_, freq, tmst, each_, fhour from cte where init + each_ <= 23
)
select freq,tmst,convert(time, right('0' + convert(varchar(2),init), 2) + ':00:00')
from cte order by freq,init,each_
Remember to continue using the #data table.
Output:

Answer 3

First drop any temp tables that have the names of the temp tables you will create:
IF OBJECT_ID(N'tempdb..#Interval', N'U') IS NOT NULL DROP TABLE #Interval
GO
IF OBJECT_ID(N'tempdb..#Interval2', N'U') IS NOT NULL DROP TABLE #Interval2
GO
IF OBJECT_ID(N'tempdb..#Runstart', N'U') IS NOT NULL DROP TABLE #Runstart
GO
Then create, and insert data into, your temp tables:
CREATE TABLE #Interval
(
_Time NVARCHAR(13),
NextRunTime DATETIME
)
GO
INSERT INTO #Interval VALUES ('Every 3 hours','2019-06-03 10:00:00')
INSERT INTO #Interval VALUES ('Every 3 hours','2019-05-28 20:00:00')
INSERT INTO #Interval VALUES ('Every 4 hours','2017-07-31 18:00:00')
INSERT INTO #Interval VALUES ('Every 1 hours','2019-06-03 14:00:00')
INSERT INTO #Interval VALUES ('Every 4 hours','2017-06-08 16:00:00')
GO
CREATE TABLE #Interval2
(
RunID INT IDENTITY(10001,1) NOT NULL PRIMARY KEY,
_Time INT NOT NULL,
NextRunTime DATETIME NOT NULL
)
GO
The code below ensures that you get the right interval for each run start, note: If the number of hours are ever 10 or more, it would be necessary to add some more code here to make the number of digits selected conditional upon the length of the string which contains them, let me know if you need this code too.
INSERT INTO #Interval2 (_TIME,NextRunTime) SELECT SUBSTRING(_Time,7,1),NextRunTime FROM #Interval WHERE LEFT(_Time,5) = 'Every'
GO
CREATE TABLE #Runstart
(
StartID INT IDENTITY(10001,1) NOT NULL PRIMARY KEY,
RunID INT NOT NULL,
[Start_DTTM] DATETIME
)
GO
Next populate the #RUNSTART table using this loop:
DECLARE #RunID INT = 10001
DECLARE #RunTime INT = (SELECT _TIME FROM #Interval2 WHERE RunID = #RunID)
DECLARE #NextRun DATETIME = (SELECT NextRunTime FROM #Interval2 WHERE RunID = #RunID)
WHILE #RunID <= (SELECT MAX(RunID) FROM #Interval2)
BEGIN
WHILE #NextRun < (SELECT DATEADD(DD,1,NextRunTime) FROM #Interval2 WHERE RunID = #RunID)
BEGIN
INSERT INTO #Runstart (RunID,[Start_DTTM]) SELECT #RunID,DATEADD(HH,#RunTime,#NextRun)
SET #NextRun = (SELECT DATEADD(HH,#RunTime,#NextRun))
END
SET #RunID = #RunID+1
SET #RunTime = (SELECT _TIME FROM #Interval2 WHERE RunID = #RunID)
SET #NextRun = (SELECT NextRunTime FROM #Interval2 WHERE RunID = #RunID)
END
GO
SELECT StartID, RunID,CONVERT(VARCHAR,START_DTTM,108) AS Start_time FROM #RUNSTART