Thread: include ids in query grouped by multipe values
Hi Group,
for several days I have been trying to resolve the following task below, but all my attempts so far appear to give me back too many rows:
I have data kind like this in TableA:
id IDone IDtwo sale
1 010 200 8000
2 010 200 7851
3 010 200 517
4 020 210 5730
5 020 210 2000
6 020 230 3170
7 020 230 3170
8 020 230 2051
9 030 230 0
With the query below I can basically select the maximum sale for each IDone - IDtwo combination - so almost what I need:
select IDone, IDtwo, max(sale) as maxsale FROM TableA group by IDone, IDtwo;
But it would want to also select the id column ( and all other additonal 20 columns of TabelA not shown above) and need that there is only one record returned for each IDone - IDtwo combination. I tried
SELECT a.id, a.IDone, a.IDtwo, a.sale FROM TableA a
inner join ( select IDone, IDtwo, max(sale) as maxsale FROM TableA group by IDone, IDtwo ) b
on a.IDone = b.IDone and b.IDtwo = b.IDtwo
and a.sale = b.maxsale;
and a.sale = b.maxsale;
but that returns too many rows and I do not understand why
How can I resolve this ?
Karsten Vennemann
Terra GIS LTD
Terra GIS LTD
Hi Karsten
--
2014-02-17 14:49 GMT-05:00 karsten <karsten@terragis.net>:
If you only want the first one, you could do something like:
SELECT min(a.id) as id, a.IDone, a.IDtwo, a.sale
FROM TableA a
INNER JOIN (SELECT IDone, IDtwo, max(sale) AS maxsale FROM TableA GROUP BY IDone, IDtwo) b
ON a.IDone = b.IDone
AND a.IDtwo = b.IDtwo
AND a.sale = b.maxsale
GROUP BY a.IDone, a.IDtwo, a.sale;
but that returns too many rows and I do not understand why
It returns more than the expected rows because there can be multiple rows fulfilling the conditions (in the example, rows with id 6 and 7 will both appear as both have the max(sale) for idone = 020 and idtwo = 230)
How can I resolve this ?
It depends if you want to show all the rows with max(sale) (which you're already doing so I suppose you don't want that), if you want to show the first one to be found or if you want to show the last one to be found.
SELECT min(a.id) as id, a.IDone, a.IDtwo, a.sale
FROM TableA a
INNER JOIN (SELECT IDone, IDtwo, max(sale) AS maxsale FROM TableA GROUP BY IDone, IDtwo) b
ON a.IDone = b.IDone
AND a.IDtwo = b.IDtwo
AND a.sale = b.maxsale
GROUP BY a.IDone, a.IDtwo, a.sale;
and add the other columns as desired
--
Karsten-3-2 wrote > select IDone, IDtwo, max(sale) as maxsale FROM TableA group by IDone, > IDtwo; > > But it would want to also select the id column ( and all other additonal > 20 > columns of TabelA not shown above) and need that there is only one record > returned for each IDone - IDtwo combination. I tried > > SELECT a.id, a.IDone, a.IDtwo, a.sale FROM TableA a > inner join ( select IDone, IDtwo, max(sale) as maxsale FROM TableA group > by > IDone, IDtwo ) b > on a.IDone = b.IDone and b.IDtwo = b.IDtwo > and a.sale = b.maxsale; > [Not Tested] SELECT b.IDone, b.IDtwo, b.sale, array_agg(a) AS matching_on_tableA FROM TableA a NATURAL JOIN ( SELECT IDone, IDtwo, max(sale) AS sale FROM TableA GROUP BY 1, 2 ) b GROUP BY 1, 2, 3; In this solution you simply save the entire tableA record, as a composite typed column, into an array so that you now have a single row for each "IDone, IDtwo, (max)sale" combination - which you omitted in the description above - but can still access to relevant matching rows using the array. Add "ORDER BY" - e.g., array_agg(...ORDER BY) - to setup a desired sort order. You can do something like (against, not tested): SELECT IDone, IDtwo, sale, (array_agg[0]).* AS row_from_tablea FROM <the above query> to get to the relevant data in the array. David J. -- View this message in context: http://postgresql.1045698.n5.nabble.com/include-ids-in-query-grouped-by-multipe-values-tp5792470p5792491.html Sent from the PostgreSQL - sql mailing list archive at Nabble.com.