Only return rows with local max [duplicate] - sql

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Closed 11 months ago.
The code below gives me something similar to the table below. What I am looking to do is only return the PROVID that has the max count per PATID.
SELECT PAT_ID AS PATID
, VISIT_PROV_ID AS PROVID
, COUNT(*) AS PROVCOUNT
FROM PAT_ENC
GROUP BY PAT_ID, VISIT_PROV_ID
ORDER BY PAT_ID, COUNT(*) DESC
PATID
PROVID
PROVCOUNT
1
3
1
2
4
6
2
3
2
2
8
1
3
4
6
4
1
8
4
2
3
The table below would be the desired result based on the same data from the previous table.
PATID
PROVID
PROVCOUNT
1
3
1
2
4
6
3
4
6
4
1
8

Answer 1

We can user RANK() OVER (PARTITION BY PATID ORDER BY PROVCOUNT DESC), which gives a ranking of 1 to the row with largest value of PROVCOUNT for each PATID, in a CTE and then use WHERE ranking = 1 to only show these largest values
create table PAT_ENC (
PATID int,
PROVID int,
PROVCOUNT int);
INSERT INTO PAT_ENC (PATID, PROVID, PROVCOUNT)
SELECT 1, 3, 1 FROM DUAL UNION ALL
SELECT 2, 4, 6 FROM DUAL UNION ALL
SELECT 2, 3, 2 FROM DUAL UNION ALL
SELECT 2, 8, 1 FROM DUAL UNION ALL
SELECT 3, 4, 6 FROM DUAL UNION ALL
SELECT 4, 1, 8 FROM DUAL UNION ALL
SELECT 4, 2, 3 FROM DUAL;
WITH COUNTED AS
(SELECT
PATID,
PROVID,
PROVCOUNT,
RANK() OVER (PARTITION BY PATID ORDER BY PROVCOUNT DESC) ranking
FROM PAT_ENC)
SELECT
PATID,
PROVID,
PROVCOUNT
FROM COUNTED
WHERE ranking = 1;
PATID | PROVID | PROVCOUNT
----: | -----: | --------:
1 | 3 | 1
2 | 4 | 6
3 | 4 | 6
4 | 1 | 8
db<>fiddle here