How to use group by and partion together in pgsql

Question

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How Do I remove duplicate x,y,z per location first and count duplicated x,y,zs throughout all locations.

What I have tried:

SELECT x, y, z, name, number, count_ 
    FROM
            (SELECT x,y,z,name, number, count(*)
            OVER
                (PARTITION BY
                x,
                y,
                z
                ) AS count_
                       FROM locations AS ml
		               JOIN locs AS ma ON ma.locid= ml.locid GROUP BY x,y,z,lomdrivename) tableWithCount WHERE ORDER BY count_ desc

Posted 13-Oct-21 19:23pm

Erkhembayar Enkhtaivan

Updated 14-Oct-21 21:29pm

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Jörgen Andersson · Answer 1 · 2021-10-14T21:29:00

Keep in mind that Group By happens before Aggregation OVER PARTITION BY.
So the best way is to only use one of them at a time

SQL

WITH Agg AS (
    SELECT  x
           ,y
           ,z
           ,name
           ,number
           ,count(*) OVER (PARTITION BY x,y,z ORDER BY ?) AS count_
           ,ROW_NUMBER() OVER (PARTITION BY x,y,z ORDER BY ?) AS rn
    FROM    locations AS ml
    JOIN    locs AS ma ON ma.locid = ml.locid
    )
SELECT  x
       ,y
       ,z
       ,name
       ,number
       ,count_
FROM    Agg
WHERE   rn = 1

Adjust as needed.
And keep in mind that you always need a field(s) to order by when you partition