Unable to get the required result using update statement - sql

Question

I am unable to update the data using record by record below scenario.
Required output: patient will able to Admit/Re-admit multiple times in hospital, if a patient readmitted multiple times in hospital after the first visit, first visit record will get Re-admission=0 and Index=1. This visit should cal Index_Admission of that patient. using this index_admission should calculate the 30-day readmission.
Current Output:
Calculation:
From index_admission discharge date to next admit_visit date,
1) if the diff is having less than 30 days, readmission=1 and Index=0
else readmission=0 and Index=1 should be update.
For checking this every time should check using the latest index_admission discharge_date.
To get this result i written below logic, but it's updating readmission=0 and Index=1 after 30-day post discharge of using first index admission.
UPDATE Readmission
SET Index_AMI = (CASE
WHEN DATEDIFF(DD, (SELECT
Sub.Max_Index_Dis
FROM (SELECT
Patient_ID,
MAX(Discharge_Date_Time) Max_Index_Dis
FROM Readmission
WHERE Index_AMI = 1 AND FPR.Patient_ID = Patient_ID
GROUP BY Patient_ID) Sub), FPR.Admit_Date_Time) <= 31 THEN 0 ELSE 1
END),
Is_AMI_Readmission = (CASE
WHEN DATEDIFF(DD, (SELECT
Sub.Max_Index_Dis
FROM (SELECT
Patient_ID,
MAX(Discharge_Date_Time) Max_Index_Dis
FROM Readmission
WHERE Index_AMI = 1 AND FPR.Patient_ID = Patient_ID
GROUP BY Patient_ID) Sub)
, FPR.Admit_Date_Time) <= 31 THEN 1 ELSE 0
END)
FROM Readmission FPR
WHERE fpr.index_ami IS NULL
Expected Result:
Please help me to resolve the issue.
Best Regards,
Nagendra

Answer 1

Thank you all for trying to help.
I some how managed to solve it using temporary tables.
If there is any issues, especially performance, with this approach please feel free to comment/criticize.
/*------------ To moving all Patient_Readmission data into temp table -------------*/
IF EXISTS (select * FROM tempdb.dbo.sysobjects o
WHERE o.xtype IN ('U')
AND o.id = OBJECT_ID(N'tempdb..#Readmission')
)
Begin
DROP TABLE #Readmission
End
IF NOT EXISTS (SELECT * FROM tempdb.dbo.sysobjects o
WHERE o.xtype IN ('U')
AND o.id = OBJECT_ID(N'tempdb..#Readmission')
)
BEGIN
select Patient_ID,ID,Encounter_Code
,Admit_Date_Time,Discharge_Date_Time
,Is_AMI_Readmission,Index_AMI
into #Readmission
from Patient_Readmission
END
GO
/*----------- To get Max Index discharge_date for all patients where index=1----------*/
IF EXISTS (select * FROM tempdb.dbo.sysobjects o
WHERE o.xtype IN ('U')
AND o.id = OBJECT_ID(N'tempdb..#Each_Pt_Max_Dsrg')
)
Begin
DROP TABLE #Each_Pt_Max_Dsrg
End
IF NOT EXISTS (SELECT * FROM tempdb.dbo.sysobjects o
WHERE o.xtype IN ('U')
AND o.id = OBJECT_ID(N'tempdb..#Each_Pt_Max_Dsrg')
)
BEGIN
select Patient_ID,Index_AMI,Max(Discharge_Date_Time) Max_Index_Dis
into #Each_Pt_Max_Dsrg
from #Readmission where Index_AMI=1 group by Patient_ID,Index_AMI
END
Declare #var int
Set #var=(select Min(Patient_ID) from #Each_Pt_Max_Dsrg)
While #var is not null
Begin
Declare #Var_En int
declare #maxDisch datetime
Set #Var_En=(Select Min(ID) From #Readmission Where Index_AMI Is null and Patient_ID=#var)
While #Var_En is Not NULL
Begin
set #maxDisch = dateadd(dd,-1,(select max(Max_Index_Dis) from #Each_Pt_Max_Dsrg where Index_AMI=1 and Patient_ID=#var))
while (#maxDisch < (select max(Max_Index_Dis) from #Each_Pt_Max_Dsrg where Index_AMI=1 and Patient_ID=#var))
begin
Update #Readmission
set Index_AMI=(Case When Datediff(DD,(Select Max(Max_Index_Dis) From #Each_Pt_Max_Dsrg Where Index_AMI=1 And Patient_ID=#var),FPR.Admit_Date_Time) between 0 and 31 Then 0 Else 1 End)
,Is_AMI_Readmission=(Case When Datediff(DD,(Select Max(Max_Index_Dis) From #Each_Pt_Max_Dsrg Where Index_AMI=1 And Patient_ID=#var),FPR.Admit_Date_Time) between 0 and 31 Then 1 Else 0 End)
From #Readmission FPR where Patient_ID=#var and ID=#Var_En and Index_AMI is NULL
set #maxDisch = (select max(Max_Index_Dis) from #Each_Pt_Max_Dsrg where Index_AMI=1 and Patient_ID=#var)
delete from #Each_Pt_Max_Dsrg
insert into #Each_Pt_Max_Dsrg
select Patient_ID,Index_AMI,Max(Discharge_Date_Time) Max_Index_Dis
from #Readmission where Index_AMI=1 group by Patient_ID,Index_AMI
end
SET #Var_En = (SELECT Min(ID) FROM #Readmission WHERE ID> #Var_En)
End
SET #Var = (SELECT MIN(Patient_ID) FROM #Each_Pt_Max_Dsrg WHERE Patient_ID > #var)
End