Exclude records that meet certain criteria by row - sql

Question

I'm in need of some brainstorming. I have built a query that shows me what I need. However the ask now is to use this list of records and exclude records based on a certain criteria.
This is my current output from the query built:
Patient | Action | Date
james | REG | 2019/01/01
James | CUR | 2019/01/15
Jacon | REG | 2019/01/12
Jacob | REG | 2019/01/13
Main | CUR | 2019/01/01
Main | REG | 2019/01/05
Lucy | REG | 2019/01/08
Lucy | CUR | 2019/01/09
Lucy | CUR | 2019/01/10
Based on the sample data from above I want to remove any patients where the first record is 'REG' and the following Action is 'CUR'. So in this example I only want to remove James.
Any Ideas on what I should do?
Thank you for your help!

Answer 1

Please group your data first by using dense_rank and row_number, then benefiting from temp tables, get the data you are looking for.
CREATE TABLE #temp (Patient VARCHAR(50), Action VARCHAR(3))
Insert INTO #temp VALUES
('james','REG'),
('james','CUR'),
('Jacob','REG'),
('Jacob','REG'),
('Main','CUR'),
('Main','REG'),
('Lucy','REG'),
('Lucy','CUR'),
('Lucy','CUR')
SELECT *, DENSE_RANK() OVER (ORDER BY Patient ASC) GroupNo,
ROW_NUMBER() OVER (partition BY Patient ORDER BY Patient ASC) GroupOrder
INTO #PatientsWithGroup
FROM #temp
SELECT MIN(c1.GroupNo) GroupNo
INTO #PatsToEliminate
FROM #PatientsWithGroup c1
INNER JOIN #PatientsWithGroup c2 ON c1.GroupNo=c2.GroupNo
WHERE (c1.GroupOrder=1 AND c1.Action='REG') AND (c2.GroupOrder = 2 AND c2.Action='CUR')
HAVING COUNT(c1.Patient)<3
SELECT *
FROM #PatientsWithGroup p
WHERE p.GroupNo NOT IN (SELECT GroupNo FROM #PatsToEliminate)

Answer 2

You can use the LEAD function to look ahead.
CREATE TABLE #Patients (
ID int IDENTITY(1,1),
Patient varchar(50),
[Action] varchar(50)
);
INSERT INTO #Patients (Patient, [Action])
VALUES
('james', 'REG'),
('James', 'CUR'),
('Jacon', 'REG'),
('Jacob', 'REG'),
('Main', 'CUR'),
('Main', 'REG'),
('Lucy', 'REG'),
('Lucy', 'CUR'),
('Lucy', 'CUR');
SELECT * FROM #Patients;
WITH
PatientWithNextAction AS (
SELECT
Patient,
[Action],
LEAD([Action]) OVER(PARTITION BY Patient ORDER BY ID) NextAction
FROM
#Patients
)
DELETE
FROM
#Patients
WHERE
Patient IN (
SELECT
Patient
FROM
PatientWithNextAction
WHERE
[Action] = 'REG'
AND NextAction = 'CUR'
);
SELECT * FROM #Patients;
DROP TABLE #Patients;

Answer 3

Try this:
select 1 as ordre, 'james' as Patient, 'REG' as Action into #tmp
union select 2,'James', 'CUR'
union select 3,'Jacon', 'REG'
union select 4,'Jacob', 'REG'
union select 5,'Main' , 'CUR'
union select 6,'Main' , 'REG'
union select 7,'Lucy' , 'REG'
union select 8,'Lucy' , 'CUR'
union select 9,'Lucy' , 'CUR'
;with cte as
(
select ordre, Patient, [Action], RANK () OVER (
PARTITION BY Patient
ORDER BY ordre
) Patient_order from #tmp a
)
select * from cte a where not exists(select 1 from cte b where a.Patient = b.Patient and b.Patient_order = 1 and Action = 'REG'
and exists(select 1 from cte c where c.Patient = b.Patient and c.Patient_order = 2 and Action = 'CUR')
)