How to de-duplicate SQL table rows by multiple columns with hierarchy? - sql

Question

I have a table with multiple records for each patient.
My end goal is a table that is 1-to-1 between Patient_id and Value.
I would like to de-duplicate (in respect to patient_id) my rows based on "a hierarchical series of aggregate functions" (if someone has a better way to phrase this, I'd appreciate that as well.)
+----+------------+------------+------------+----------+-----------------+-------+
| ID | patient_id | Date | Date2 | Priority | Source | Value |
+----+------------+------------+------------+----------+-----------------+-------+
| 1 | 1 | 2017-09-09 | 2018-09-09 | 1 | 'verified' | 55 |
| 2 | 1 | 2017-09-09 | 2018-11-11 | 2 | 'verified' | 78 |
| 3 | 1 | 2017-11-11 | 2018-09-09 | 3 | 'verified' | 23 |
| 4 | 1 | 2017-11-11 | 2018-11-11 | 1 | 'self_reported' | 11 |
| 5 | 1 | 2017-09-09 | 2018-09-09 | 2 | 'self_reported' | 90 |
| 5 | 1 | 2017-09-09 | 2018-09-09 | 3 | 'self_reported' | 34 |
| 6 | 2 | 2017-11-11 | 2018-09-09 | 2 | 'self_reported' | 21 |
+----+------------+------------+------------+----------+-----------------+-------+
For each patient_id, I would like to get the row(s) that has/have the MAX(Date). In the case that there are still duplicated patient_id, I would like to get the row(s) with the MIN(Priority). In the case that there are still duplicated rows I would like to get the row(s) with the MIN(Date2).
The way I've approached this problem is using a series of queries like this to de-duplicate on the columns one at a time.
SELECT *
FROM #table t1
LEFT JOIN
(SELECT
patient_id,
MIN(priority) AS min_priority
FROM #table
GROUP BY patient_id) t2 ON t2.patient_id = t1.patient_id
WHERE t2.min_priority = t1.priority
Is there a way to do this that allows me to de-dup on multiple columns at once? Is there a more elegant way to do this?
I'm able to get my results, but my solution feels very inefficient, and I keep running into this. Thank you for any input.

Answer 1

You could use row_number(), if your RDBMS supports it:
select ID, patient_id, Date, Date2, Priority, Source, Value
from (
select
t.*,
row_number() over(partition by patient_id order by Date desc, Priority, Date2) rn
from mytable t
) where rn = 1
Another option is to filter with a correlated subquery that sorts the record according to your criteria, like so:
select t.*
from mytable t
where id = (
select id
from mytable t1
where t1.patient_id = t.patient_id
order by t1.Date desc, t1.Priority, t1.Date2
limit 1
)
The actual syntax for limit varies accross RDBMS.