Complicated SQL question

Hi Experts,
I have a table containing the following:

ID
PatientID
EffectiveFrom (DateTime) Start of service
EffectiveTo (DateTime) End of service

Now I need to get the total count of patients serviced between a given date range, however (here goes the catch..) if a patient has 30 days or more between the one end of service (EffectiveTo) and the next start of service (EffectiveFrom) it should be counted as 2.

My question is, is there a way to get this count from a query/sql view or there is a need to create a custom function to loop for all records etc..?
LVL 4
bfuchsAsked:
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HainKurtConnect With a Mentor Sr. System AnalystCommented:
after "from patients as P1"

select count(1) as PatientCount from (
select distinct PatientID,  iif(datediff('d', EffectiveTo, nz(next_service,EffectiveTo))>30, 1, 0) as MoreThan30 from (
       select PatientID, EffectiveFrom, EffectiveTo,  
              (select min(EffectiveFrom) from patients as P2 where P2.PatientID=P1.PatientID and P2.EffectiveFrom > P1.EffectiveTo) as next_service
         from patients as P1
      where [date] between EffectiveFrom and EffectiveTo
) as x
) as y

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HainKurtSr. System AnalystCommented:
post a sample data & what you need from this sample

everything is possible :)
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Kent OlsenData Warehouse Architect / DBACommented:
Hi bfuchs,

Are you looking for the number of visits or the number of unique patients?  That is, if a patient visits multiple times during that date range, is he counted once or multiple times?
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HainKurtSr. System AnalystCommented:
save this as a query, say q_Patient_ex

select PatientID, EffectiveFrom, EffectiveTo, 
       (select min(EffectiveFrom) from patients as P2 where P2.PatientID=P1.PatientID and P2.EffectiveFrom > P1.EffectiveTo) next_service
  from patients as P1 

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test it by opening the query, or running this

select * from q_Patient_ex

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now run this

select sum(iff(datediff(d, EffectiveTo, nz(next_service, EffectiveTo))>30, 2, 1))
  from q_Patinets_X
 where @somedate between EffectiveFrom and EffectiveTo
 group by patientID

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bfuchsAuthor Commented:
Hi,

@HainKurt,
Attached sample data, The number of patients I'm expecting to get for year 2004 is 3, as patientID 100 should be counted twice since there were more then 30 days between end od 2nd service and beginning of 3rd.

@Kdo,
Lets put it this way, I need the number of visits allowances (service date ranges), however if there are less then 30 days from when a patients service date ended and started again then its counted as one.

Thanks,
Ben
Book1.xls
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HainKurtSr. System AnalystCommented:
what is this giving?

select sum(iff(datediff(d, EffectiveTo, nz(next_service, EffectiveTo))>30, 2, 1)) as Patient_Count
  from (
select PatientID, EffectiveFrom, EffectiveTo, 
       (select min(EffectiveFrom) from patients as P2 where P2.PatientID=P1.PatientID and P2.EffectiveFrom > P1.EffectiveTo) next_service
  from patients as P1 
) as q_Patinets_X
 where @somedate between EffectiveFrom and EffectiveTo

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(combined my solution into one big chunk)
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Kent OlsenData Warehouse Architect / DBACommented:
That really needs to be recursive SQL.  It could be that the visits chain to a length of 1 or many.  When 3 or more visits chain, care must be taken that only the first visit is counted.  Recursive SQL does that quite easily, but Access doesn't support it.
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bfuchsAuthor Commented:
@HainKurt,
See attached, (just replaced name of table to sheet1 as the one you gave exists).

@Kdo,
How about if I upload my data into a sql table would that help?
Untitled.png
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HainKurtSr. System AnalystCommented:
ok, here it is:

select count(1) as PatientCount from (
select distinct PatientID, MoreThan30 from (
select PatientID, iif(datediff('d', EffectiveTo, nz(next_service,EffectiveTo))>30, 1, 0) as MoreThan30 from (
       select PatientID, EffectiveFrom, EffectiveTo,  
              (select min(EffectiveFrom) from patients as P2 where P2.PatientID=P1.PatientID and P2.EffectiveFrom > P1.EffectiveTo) as next_service
         from patients as P1
) as x
) as y
) as z

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HainKurtSr. System AnalystCommented:
add a conditionbefore line 6 as

where @somedate between EffectiveFrom and EffectiveTo
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bfuchsAuthor Commented:
@HainKurt,
Actually I fixed your version re the syntax as follows
SELECT Sum(IIf(DateDiff("d",[EffectiveTo],nz([next_service],[EffectiveTo]))>30,2,1)) AS Patient_Count
FROM (select PatientID, EffectiveFrom, EffectiveTo, 
       (select min(EffectiveFrom) from sheet1 as P2 where P2.PatientID=P1.PatientID and P2.EffectiveFrom > P1.EffectiveTo) as  next_service
  from sheet1 as P1 
) AS q_Patinets_X

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However the results is 5, (while the table attached only has 4 records..and expected results is 3)
Thanks,
Ben
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HainKurtSr. System AnalystCommented:
or maybe this is better :) previous one has one more redundant select

select count(1) from (
select distinct PatientID,  iif(datediff('d', EffectiveTo, nz(next_service,EffectiveTo))>30, 1, 0) as MoreThan30 from (
       select PatientID, EffectiveFrom, EffectiveTo,  
              (select min(EffectiveFrom) from patients as P2 where P2.PatientID=P1.PatientID and P2.EffectiveFrom > P1.EffectiveTo) as next_service
         from patients as P1
) as x
) as y

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bfuchsAuthor Commented:
Ok your latest seems to work,
where do I add a date range to filter for, for example from 1/1/14 till 12/31/14?
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HainKurtSr. System AnalystCommented:
explanation:

line 3-5: I find result like

PatientID      EffectiveFrom      EffectiveTo      next_service
100      01/01/2014      01/02/2014      15/02/2014
100      15/02/2014      28/02/2014      01/04/2014
100      01/04/2014      02/04/2014      05/05/2014
200      01/01/2014      15/01/2014      
100      05/05/2014      15/05/2014      

line 2-6: here I find data like

PatientID      MoreThan30
100      0
100      1
200      0

line 1-7: here i get result
3
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bfuchsAuthor Commented:
Hi HainKurt,
It looks like working well, just waiting to get hold of production data in order to finalize..
(I can see from your icon pic how you're already smiling from this big achievement -:)
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HainKurtSr. System AnalystCommented:
i do like challenges :)
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bfuchsAuthor Commented:
Thanks HainKurt,
Great job, As said you like challenges, I will get more for you in the future:)
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bfuchsAuthor Commented:
Hi HainKurt,
I need some modification on this query, posted another question, if you have a chance, please take a look at the following,
http://www.experts-exchange.com/Database/MS_Access/Q_28586854.html
Thanks
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bfuchsAuthor Commented:
Hi HainKurt,

I am attaching a file with some data, according to the 30 days rule this should only return one record for year 2013, however your query its returning 2. (tested by running the middle part of your query), please let me know how to correct this.

Thanks,
Ben
Book1.xls
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