Use CTE to capture volume counts by day and hour - sql

Question

I want to see current patient volumes by days of the week and by hour based off of their registered Start date and Discharge date.
Ex: John doe Start date: 01-01-2022 13:00:00 ; End date 01-01-2022 16:25:00
I would like the data to show each Hour John doe is in the Facility. So output would look like something like this:
John Doe 01-01-2022 ( Hour) 13
John Doe 01-01-2022 ( Hour) 14
John Doe 01-01-2022 ( Hour) 15
John Doe 01-01-2022 ( Hour) 16
I have my start date and discharge dates in a temp table and thought I could use a CTE to get this done, but not sure how to link the CTE results to my table.
How do I get the breakdown of volumes by hour so I can count how many people are in the facility each hour based off of the start and discharge dates?
DECLARE #minDateTime AS DATETIME;
DECLARE #maxDateTime AS DATETIME;
SET #minDateTime = '2022-05-01 05:28:05.000';
SET #maxDateTime = '2022-05-02 06:50:00.000';
;
WITH Dates_CTE
AS
(SELECT #minDateTime AS Dates
UNION ALL
SELECT Dateadd(hh, 1, Dates)
FROM Dates_CTE
WHERE Dates < Dateadd(hh, -1, #maxDateTime)
)
SELECT --Convert(VARCHAR,Year,Dates)
Dates
,Year(Dates) as 'Year'
,Month(Dates) as 'Month'
,Day(Dates) as 'day'
,Datename(DW,Dates) as 'DayName'
,DATEPART(HOUR,Dates) as 'hh'
FROM Dates_CTE
OPTION (MAXRECURSION 0)
Sample Data
AccountNumber ServiceDateTime RegistrationTypeDischargeDateTime
G111 2021-05-07 10:44:19.000 2021-05-07 14:30:00.000
G222 2021-05-08 09:59:00.000 2021-05-08 10:56:00.000
G333 2021-07-02 11:35:07.000 2021-07-02 11:53:00.000
G444 2021-07-07 07:57:16.000 2021-07-07 13:35:00.000

Answer 1

If we have the enter and leave datestamp for each patient in another table we can join you calendar table and group by hour to find the id's of patients present and count them.
create table inTreatment(
patientid int,
enter datetime,
leave datetime
);
insert into inTreatment values
(1,'2022-05-01 09:00:00','2022-05-01 18:00:00'),
(2,'2022-05-01 11:00:00','2022-05-01 14:00:00'),
(3,'2022-05-01 12:00:00','2022-05-02 15:00:00')
GO
3 rows affected
DECLARE #minDateTime AS DATETIME;
DECLARE #maxDateTime AS DATETIME;
SET #minDateTime = '2022-05-01 05:00:00.000';
SET #maxDateTime = '2022-05-02 06:00:00.000';
;
WITH Dates_CTE
AS
(SELECT #minDateTime AS Dates
UNION ALL
SELECT Dateadd(hh, 1, Dates)
FROM Dates_CTE
WHERE Dates < Dateadd(hh, -1, #maxDateTime)
)
SELECT --Convert(VARCHAR,Year,Dates)
string_agg(patientid,',') patients,
count(patientid) no_pats,
Dates
--,Year(Dates) as 'Year'
--,Month(Dates) as 'Month'
--,Day(Dates) as 'day'
----,Datename(DW,Dates) as 'DayName'
--,DATEPART(HOUR,Dates) as 'hh'
FROM Dates_CTE d
left join InTreatment i
on enter <= Dates and leave >= Dates
group by dates
OPTION (MAXRECURSION 0)
GO
patients | no_pats | Dates
:------- | ------: | :----------------------
null | 0 | 2022-05-01 05:00:00.000
null | 0 | 2022-05-01 06:00:00.000
null | 0 | 2022-05-01 07:00:00.000
null | 0 | 2022-05-01 08:00:00.000
1 | 1 | 2022-05-01 09:00:00.000
1 | 1 | 2022-05-01 10:00:00.000
1,2 | 2 | 2022-05-01 11:00:00.000
1,2,3 | 3 | 2022-05-01 12:00:00.000
1,2,3 | 3 | 2022-05-01 13:00:00.000
1,2,3 | 3 | 2022-05-01 14:00:00.000
1,3 | 2 | 2022-05-01 15:00:00.000
1,3 | 2 | 2022-05-01 16:00:00.000
1,3 | 2 | 2022-05-01 17:00:00.000
1,3 | 2 | 2022-05-01 18:00:00.000
3 | 1 | 2022-05-01 19:00:00.000
3 | 1 | 2022-05-01 20:00:00.000
3 | 1 | 2022-05-01 21:00:00.000
3 | 1 | 2022-05-01 22:00:00.000
3 | 1 | 2022-05-01 23:00:00.000
3 | 1 | 2022-05-02 00:00:00.000
3 | 1 | 2022-05-02 01:00:00.000
3 | 1 | 2022-05-02 02:00:00.000
3 | 1 | 2022-05-02 03:00:00.000
3 | 1 | 2022-05-02 04:00:00.000
3 | 1 | 2022-05-02 05:00:00.000
db<>fiddle here

Answer 2

Given this table and sample data:
CREATE TABLE dbo.Admissions
(
AccountNumber char(4),
ServiceDateTime datetime,
RegistrationTypeDischargeDateTime datetime
);
INSERT dbo.Admissions VALUES
('G111','20210507 10:44:19','20210507 14:30:00');
Here's how I would do it:
DECLARE #min datetime = '20210507 05:28:05',
#max datetime = '20210508 06:50:00';
DECLARE #d tinyint = DATEDIFF(HOUR, #min, #max),
#floor datetime = SMALLDATETIMEFROMPARTS
(YEAR(#min), MONTH(#min), DAY(#min), DATEPART(HOUR, #min), 0);
; -- see sqlblog.org/cte
WITH hours(h) AS
(
SELECT #floor UNION ALL
SELECT DATEADD(HOUR, 1, h)
FROM hours WHERE h <= #max
)
SELECT a.AccountNumber, Date = CONVERT(date, hours.h),
Hour = DATEPART(HOUR, hours.h)
FROM hours INNER JOIN dbo.Admissions AS a
ON a.ServiceDateTime < DATEADD(HOUR, 1, hours.h)
AND a.RegistrationTypeDischargeDateTime >= hours.h
OPTION (MAXRECURSION 32767);
Output:
AccountNumber
Date
Hour
G111
2021-05-07
10
G111
2021-05-07
11
G111
2021-05-07
12
G111
2021-05-07
13
G111
2021-05-07
14
Example db<>fiddle
You may need to tweak <=/</>=/> depending on how you want to handle edge cases (e.g. entry or exit right on the hour, or entry and exit < 1 hour).

Answer 3

For a fast, simple way (vs CTE) CROSS APPLY using a numbers table or a tally function. In this case I'm using dbo.fnTally
select a.AccountNumber, cast(a.ServiceDateTime as date) [Date],
datepart(hour, dateadd(hour, fn.N, cast(a.ServiceDateTime as time))) hr
from #Admissions a
cross apply dbo.fnTally(0, datediff(hour,
a.ServiceDateTime,
a.RegistrationTypeDischargeDateTime)) fn;
dbo.fnTally
CREATE FUNCTION [dbo].[fnTally]
/**********************************************************************************************************************
Jeff Moden Script on SSC: https://www.sqlservercentral.com/scripts/create-a-tally-function-fntally
**********************************************************************************************************************/
(#ZeroOrOne BIT, #MaxN BIGINT)
RETURNS TABLE WITH SCHEMABINDING AS
RETURN WITH
H2(N) AS ( SELECT 1
FROM (VALUES
(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
,(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)
)V(N)) --16^2 or 256 rows
, H4(N) AS (SELECT 1 FROM H2 a, H2 b) --16^4 or 65,536 rows
, H8(N) AS (SELECT 1 FROM H4 a, H4 b) --16^8 or 4,294,967,296 rows
SELECT N = 0 WHERE #ZeroOrOne = 0 UNION ALL
SELECT TOP(#MaxN)
N = ROW_NUMBER() OVER (ORDER BY N)
FROM H8
;