SQL lag window and custom logic [closed] - sql

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I am working on this dataset
https://dbfiddle.uk/?rdbms=sqlserver_2014&fiddle=447a5d2c33b04346e70dab0a8d098655
Custom logic:
Grouped by name, testcentre, coursename, testtype.
If a retest is taken, then scores are compared - if higher the highest one precedes or original score.
Lag:
Based on above selected row, if a lag window exists between the remaining set of records example within 4 days , then the higest score record shall be picked up.
Any suggestions is appreciated.
Sample data
+----------+-------+------------+------------+----------+-----------+------------+------------+------------------+-----------------------------------------------+
| recordid | Name | testcentre | coursename | testtype | testscore | testdate | retestflag | Preferred_Output | RejectReason |
+----------+-------+------------+------------+----------+-----------+------------+------------+------------------+-----------------------------------------------+
| 1 | Sam | Paris | English | IELTS | 90 | 01/02/2019 | 0 | 0 | |
| 3 | Sam | Paris | English | IELTS | 95 | 02/02/2019 | 1 | 1 | Better score in retest |
| 4 | Sam | Paris | English | TOEFL | 80 | 04/02/2019 | 0 | 0 | Within 4 days of previous test |
| 21 | Sam | Paris | English | IELTS | 95 | 02/02/2018 | 1 | 1 | marked as retest without base.needs inclusion |
| 5 | Jack | London | English | IELTS | 90 | 01/02/2019 | 0 | 1 | Same or bad score in retest |
| 8 | Jack | London | English | IELTS | 90 | 02/02/2019 | 1 | 0 | Same or bad score in retest |
| 7 | Louis | Brazil | English | IELTS | 70 | 01/02/2019 | 0 | 1 | Same score in retest |
| 11 | Louis | Brazil | English | IELTS | 70 | 02/02/2019 | 1 | 0 | Same score in retest |
| 13 | Louis | Brazil | English | TOEFL | 100 | 04/02/2019 | 0 | 0 | Within 4 days of previous test |
| 55 | Sam | Paris | English | IELTS | 90 | 01/02/2016 | 0 | 1 | Older test, no follow on |
| 60 | Sam | Paris | English | IELTS | 95 | 01/08/2019 | 0 | 1 | same score in retest |
| 61 | Sam | Paris | English | IELTS | 95 | 02/08/2019 | 1 | 0 | |
| 62 | Sam | Paris | English | TOEFL | 80 | 04/01/2020 | 0 | 1 | More than 4 days, included |
+----------+-------+------------+------------+----------+-----------+------------+------------+------------------+-----------------------------------------------+
Desired Output
+----------+-------+------------+------------+----------+-----------+------------+------------+------------------+
| recordid | Name | testcentre | coursename | testtype | testscore | testdate | retestflag | Preferred_Output |
+----------+-------+------------+------------+----------+-----------+------------+------------+------------------+
| 3 | Sam | Paris | English | IELTS | 95 | 02/02/2019 | 1 | 1 |
| 21 | Sam | Paris | English | IELTS | 95 | 02/02/2018 | 1 | 1 |
| 5 | Jack | London | English | IELTS | 90 | 01/02/2019 | 0 | 1 |
| 7 | Louis | Brazil | English | IELTS | 70 | 01/02/2019 | 0 | 1 |
| 55 | Sam | Paris | English | IELTS | 90 | 01/02/2016 | 0 | 1 |
| 60 | Sam | Paris | English | IELTS | 95 | 01/08/2019 | 0 | 1 |
| 62 | Sam | Paris | English | TOEFL | 80 | 04/01/2020 | 0 | 1 |
+----------+-------+------------+------------+----------+-----------+------------+------------+------------------+

Answer 1

Based on your sample data and description, this seems to do what you want:
select t.*
from (select t.*,
row_number() over (partition by name, testcentre, coursename, testtype order by testscore desc) as seqnum,
count(*) over (partition by name, testcentre, coursename, testtype) as cnt
from test t
) t
where seqnum = 1 and cnt >= 2;
This does not include the condition on "within 4 days", because that condition is not clearly explained. What happens if there are a series of 5 tests, each 3 days apart, for instance?

Answer 2

select * from (
select *, row_number() over (partition by name order by testscore desc) rn
from test
) t
where rn = 1
Fiddle