SQL calculate number of days of residency by month, by user, by location - sql

Question

I'm working on a query for a rehab organization where tenants (client/patients) live in a building when they first arrive, as they progress in their treatment they move to another building and as they near the end of treatment they are in a third building.
For funding purposes we need to know how many nights a tenant spent in each building in each month.
I can use DateDiff to get the total number of nights, but how do I get the total for each client in each month in each building?
For example, John Smith is in Building A 9/12-11/3; moves to Building B 11/3-15; moves to Building C on and is still there: 11/15 - today
What query returns a result that show the number of nights he spent in:
Building A in Septmeber, October and November.
Buidling B in November
Building C in November
Two tables hold the client's name, building name and move-in date and move-out date
CREATE TABLE [dbo].[clients](
[ID] [nvarchar](50) NULL,
[First_Name] [nvarchar](100) NULL,
[Last_Name] [nvarchar](100) NULL
) ON [PRIMARY]
--populate w/ two records
insert into clients (ID,First_name, Last_name)
values ('A2938', 'John', 'Smith')
insert into clients (ID,First_name, Last_name)
values ('A1398', 'Mary', 'Jones')
CREATE TABLE [dbo].[Buildings](
[ID_U] [nvarchar](50) NULL,
[Move_in_Date_Building_A] [datetime] NULL,
[Move_out_Date_Building_A] [datetime] NULL,
[Move_in_Date_Building_B] [datetime] NULL,
[Move_out_Date_Building_B] [datetime] NULL,
[Move_in_Date_Building_C] [datetime] NULL,
[Move_out_Date_Building_C] [datetime] NULL,
[Building_A] [nvarchar](50) NULL,
[Building_B] [nvarchar](50) NULL,
[Building_C] [nvarchar](50) NULL
) ON [PRIMARY]
-- Populate the tables with two records
insert into buildings (ID_U,Move_in_Date_Building_A,Move_out_Date_Building_A, Move_in_Date_Building_B,
Move_out_Date_Building_B, Move_in_Date_Building_C, Building_A, Building_B, Building_C)
VALUES ('A2938','2010-9-12', '2010-11-3','2010-11-3','2010-11-15', '2010-11-15', 'Kalgan', 'Rufus','Waylon')
insert into buildings (ID_U,Move_in_Date_Building_A,Building_A)
VALUES ('A1398','2010-10-6', 'Kalgan')
Thanks for your help.

Answer 1

I'd use a properly normalized database schema, your Buildings table is not useful like this. After splitting it up I believe that getting your answer will be pretty easy.
Edit (and updated): Here's a CTE which will take this strange table structure and split it into a more normalized form, displaying the user id, building name, move in and move out dates. By grouping on the ones you want (and using DATEPART() etc.) you should be able to get the data you need with that.
WITH User_Stays AS (
SELECT
ID_U,
Building_A Building,
Move_in_Date_Building_A Move_In,
COALESCE(Move_out_Date_Building_A, CASE WHEN ((Move_in_Date_Building_B IS NULL) OR (Move_in_Date_Building_C<Move_in_Date_Building_B)) AND (Move_in_Date_Building_C>Move_in_Date_Building_A) THEN Move_in_Date_Building_C WHEN Move_in_Date_Building_B>=Move_in_Date_Building_A THEN Move_in_Date_Building_B END, GETDATE()) Move_Out
FROM dbo.Buildings
WHERE Move_in_Date_Building_A IS NOT NULL
UNION ALL
SELECT
ID_U,
Building_B,
Move_in_Date_Building_B,
COALESCE(Move_out_Date_Building_B, CASE WHEN ((Move_in_Date_Building_A IS NULL) OR (Move_in_Date_Building_C<Move_in_Date_Building_A)) AND (Move_in_Date_Building_C>Move_in_Date_Building_B) THEN Move_in_Date_Building_C WHEN Move_in_Date_Building_A>=Move_in_Date_Building_B THEN Move_in_Date_Building_A END, GETDATE())
FROM dbo.Buildings
WHERE Move_in_Date_Building_B IS NOT NULL
UNION ALL
SELECT
ID_U,
Building_C,
Move_in_Date_Building_C,
COALESCE(Move_out_Date_Building_C, CASE WHEN ((Move_in_Date_Building_B IS NULL) OR (Move_in_Date_Building_A<Move_in_Date_Building_B)) AND (Move_in_Date_Building_A>Move_in_Date_Building_C) THEN Move_in_Date_Building_A WHEN Move_in_Date_Building_B>=Move_in_Date_Building_C THEN Move_in_Date_Building_B END, GETDATE())
FROM dbo.Buildings
WHERE Move_in_Date_Building_C IS NOT NULL
)
SELECT *
FROM User_Stays
ORDER BY ID_U, Move_In
This query run on your sample data produces he following output:
ID_U Building Move_In Move_Out
-------- ----------- ----------------------- -----------------------
A1398 Kalgan 2010-10-06 00:00:00.000 2010-11-23 18:35:59.050
A2938 Kalgan 2010-09-12 00:00:00.000 2010-11-03 00:00:00.000
A2938 Rufus 2010-11-03 00:00:00.000 2010-11-15 00:00:00.000
A2938 Waylon 2010-11-15 00:00:00.000 2010-11-23 18:35:59.050
(4 row(s) affected)
As you can see, from here on it will be much easier to isolate the days per patient or building, and also to find the records for specific months and calculate the correct stay duration in that case. Note that the CTE displays the current date for patients which are still in a building.
Edit (again): In order to get all months including their start and end dates for all relevant years, you can use a CTE like this:
WITH User_Stays AS (
[...see above...]
)
,
Months AS (
SELECT m.IX,
y.[Year], dateadd(month,(12*y.[Year])-22801+m.ix,0) StartDate, dateadd(second, -1, dateadd(month,(12*y.[Year])-22800+m.ix,0)) EndDate
FROM (
SELECT 1 IX UNION ALL
SELECT 2 UNION ALL
SELECT 3 UNION ALL
SELECT 4 UNION ALL
SELECT 5 UNION ALL
SELECT 6 UNION ALL
SELECT 7 UNION ALL
SELECT 8 UNION ALL
SELECT 9 UNION ALL
SELECT 10 UNION ALL
SELECT 11 UNION ALL
SELECT 12
)
m
CROSS JOIN (
SELECT Datepart(YEAR, us.Move_In) [Year]
FROM User_Stays us UNION
SELECT Datepart(YEAR, us.Move_Out)
FROM User_Stays us
)
y
)
SELECT *
FROM months;
So since we now have a tabular representation of all date ranges which can be of interest, we simply join this together:
WITH User_Stays AS ([...]),
Months AS ([...])
SELECT m.[Year],
DATENAME(MONTH, m.StartDate) [Month],
us.ID_U,
us.Building,
DATEDIFF(DAY, CASE WHEN us.Move_In>m.StartDate THEN us.Move_In ELSE m.StartDate END, CASE WHEN us.Move_Out<m.EndDate THEN us.Move_Out ELSE DATEADD(DAY, -1, m.EndDate) END) Days
FROM Months m
JOIN User_Stays us ON (us.Move_In < m.EndDate) AND (us.Move_Out >= m.StartDate)
ORDER BY m.[Year],
us.ID_U,
m.Ix,
us.Move_In
Which finally produces this output:
Year Month ID_U Building Days
----------- ------------ -------- ---------- -----------
2010 October A1398 Kalgan 25
2010 November A1398 Kalgan 22
2010 September A2938 Kalgan 18
2010 October A2938 Kalgan 30
2010 November A2938 Kalgan 2
2010 November A2938 Rufus 12
2010 November A2938 Waylon 8

Answer 2

-- set the dates for which month you want
Declare #startDate datetime
declare #endDate datetime
set #StartDate = '09/01/2010'
set #EndDate = '09/30/2010'
select
-- determine if the stay occurred during this month
Case When #StartDate <= Move_out_Date_Building_A and #EndDate >= Move_in_Date_Building_A
Then
(DateDiff(d, #StartDate , #enddate+1)
)
-- drop the days off the front
- (Case When #StartDate < Move_in_Date_Building_A
Then datediff(d, #StartDate, Move_in_Date_Building_A)
Else 0
End)
--drop the days of the end
- (Case When #EndDate > Move_out_Date_Building_A
Then datediff(d, #EndDate, Move_out_Date_Building_A)
Else 0
End)
Else 0
End AS Building_A_Days_Stayed
from Clients c
inner join Buildings b
on c.id = b.id_u

Answer 3

Try using a date table. For example, you could create one like so:
CREATE TABLE Dates
(
[date] datetime,
[year] smallint,
[month] tinyint,
[day] tinyint
)
INSERT INTO Dates(date)
SELECT dateadd(yy, 100, cast(row_number() over(order by s1.object_id) as datetime))
FROM sys.objects s1
CROSS JOIN sys.objects s2
UPDATE Dates
SET [year] = year(date),
[month] = month(date),
[day] = day(date)
Just modify the initial Dates population to meet your needs (on my test instance, the above yielded dates from 2000-01-02 to 2015-10-26). With a dates table, the query is pretty straight forward, something like this:
select c.First_name, c.Last_name,
b.Building_A BuildingName, dA.year, dA.month, count(distinct dA.day) daysInBuilding
from clients c
join Buildings b on c.ID = b.ID_U
left join Dates dA on dA.date between b.Move_in_Date_Building_A and isnull(b.Move_out_Date_Building_A, getDate())
group by c.First_name, c.Last_name,
b.Building_A, dA.year, dA.month
UNION
select c.First_name, c.Last_name,
b.Building_B, dB.year, dB.month, count(distinct dB.day)
from clients c
join Buildings b on c.ID = b.ID_U
left join Dates dB on dB.date between b.Move_in_Date_Building_B and isnull(b.Move_out_Date_Building_B, getDate())
group by c.First_name, c.Last_name,
b.Building_B, dB.year, dB.month
UNION
select c.First_name, c.Last_name,
b.Building_C, dC.year, dC.month, count(distinct dC.day)
from clients c
join Buildings b on c.ID = b.ID_U
left join Dates dC on dC.date between b.Move_in_Date_Building_C and isnull(b.Move_out_Date_Building_C, getDate())
group by c.First_name, c.Last_name,
b.Building_C, dC.year, dC.month

Answer 4

If you can't restructure the Building table you can create a query that will normalize it for you and allow for easier calculations:
SELECT "A" as Building, BuidlingA as Name, Move_in_Date_Building_A as MoveInDate,
Move_out_Date_Building_A As MoveOutDate
UNION
SELECT "B", BuidlingB, Move_in_Date_Building_B, Move_out_Date_Building_B
UNION
SELECT "C", BuidlingC, Move_in_Date_Building_C, Move_out_Date_Building_C