CODEWITHSUNDEEP
sql-servert-sql
Mich28
Mich28

Reputation: 519

TSQL: Continuous period for whole year / each month

I try to find all Cust who have membership for at least for one day in each month during 2018.

I came up with solution checking their membership at the beginning / middle / end end of each month like in snippet below, but trying to find more intelligent solution.

I know that I can use tally table for each of 365 days to check this but probably there is more elegant solution ? I'm bit new to SQL, I think I'm missing something in GROUPing area.

In the code snippet shown below, both Cust have at least one day membership.

Desired output: 

CustID
------
   1
  22

Code:

with data as 
(
    select * 
    from (values (1, 1,   '2017-12-11', '2018-01-16'),   (1, 22,  '2018-01-28', '2018-03-9' ), (1, 333, '2018-03-1', '2018-12-31') ,  -- island
                 (22, 1,  '2017-12-31', '2018-01-11'),   (22, 2,  '2017-2-11',  '2019-12-31')) as t (CustID, ContractID, StartDD, EndDD)     ---      
    )
    select 
        isdate(startDD), isdate(EndDD) 
    from 
        data
), gaps as 
(
    select  
        *,  
        datediff(day, lag(EndDD, 1, StartDD) over (partition by CustID order by StartDD), StartDD) as BreakDD          -- negative is island
    from 
        data
)
select 
    *, 
    datepart(month,StartDD) mmS , datepart(month,EndDD) mmE 
from 
    gaps 
    -- and was active any 1+ day during each of the 12 months in 2018    ????
where 
    1 = 1 
    /* and (cast('1/1/2018' as date) between StartDD and EndDD
            or cast('1/15/2018' as date) between StartDD and EndDD     
            or cast('1/31/2018' as date) between StartDD and EndDD)
       ---- etc..  for each month
       and (      cast('12/1/2018'  as date)   between  StartDD  and  EndDD 
              or  cast('12/15/2018' as date)   between  StartDD  and  EndDD  
              or  cast('12/31/2018' as date)   between  StartDD  and  EndDD  
           ) 
*/ 
--select CustID, max(BreakDD) Max_Days
--from gaps
--group by CustID

Upvotes: 1

Views: 216

Answers (2)

KumarHarsh
KumarHarsh

Reputation: 5094

find all Cust who have membership for at least for one day in each month during 2018

I think this mean that data must be present between '2018-01-01' and '2018-12-31' for each custid.

CREATE TABLE #t(CustID INT, ContractID INT, StartDD date, EndDD date)

INSERT INTO #t values (1, 1,   '2017-12-11', '2018-01-16'),   (1, 22,  '2018-01-28', '2018-03-9' ), (1, 333, '2018-03-1', '2018-12-31') ,  -- island
 (22, 1,  '2017-12-31', '2018-01-11'),   (22, 2,  '2017-2-11',  '2019-12-31')

declare @From Datetime='2018-01-01'
declare @To datetime='2018-12-31'

;with CTE as
(
select CustID,min(StartDD)StartDD
,max(EndDD)EndDD
from #t
group by CustID
)
select CustID,StartDD
,EndDD
from CTE
where StartDD<=@From and EndDD>=@To

This script is not tested across all sample data. But logic is clear.So it can be corrected accordingly.

So tell for what sample data it is not working.

Upvotes: 0

DineshDB
DineshDB

Reputation: 6193

Try this answer.

First create a function to return all the month and year between the given dates.

Function:

--SELECT * FROM dbo.Fn_GetMonthYear('2017-12-11','2018-01-16')
ALTER FUNCTION dbo.Fn_GetMonthYear(@StartDate  DATETIME,@EndDate    DATETIME)
RETURNS TABLE
AS

    RETURN(
    SELECT  DATEPART(MONTH, DATEADD(MONTH, x.number, @StartDate)) AS [Month]
            ,DATEPART(YEAR, DATEADD(MONTH, x.number, @StartDate)) AS [Year]
    FROM    master.dbo.spt_values x
    WHERE   x.type = 'P'        
    AND     x.number <= DATEDIFF(MONTH, @StartDate, @EndDate)
    )

Table Schema:

CREATE TABLE #t(CustID INT, ContractID INT, StartDD date, EndDD date)

INSERT INTO #t values (1, 1,   '2017-12-11', '2018-01-16'),   (1, 22,  '2018-01-28', '2018-03-9' ), (1, 333, '2018-03-1', '2018-12-31') ,  -- island
                 (22, 1,  '2017-12-31', '2018-01-11'),   (22, 2,  '2017-2-11',  '2019-12-31')

Here is the T-SQL Query for your requirement.

SELECT CustID
    ,COUNT(DISTINCT [Month]) NoOfMonths
FROM(
    SELECT * 
    FROM #t t
    CROSS APPLY dbo.Fn_GetMonthYear(StartDD,EndDD)
    )D
WHERE [Year] = 2018
GROUP BY CustID
HAVING COUNT(DISTINCT [Month])=12

Result:

CustID  NoOfMonths
1       12
22      12

Upvotes: 2

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