aggregate column of type row - aggregate

Question

I want to filter a column of rowtype and aggregate rowtypes when they have complement information.
So my data looks like that :
|col1|rowcol |
|----|--------------------------------|
|1 |{col1=2, col2=null, col3=4} |
|1 |{col1=null, col2=3, col3=null} |
|2 |{col1=7, col2=8, col3=null} |
|2 |{col1=null, col2=null, col3=56} |
|3 |{col1=1, col2=3, col3=7} |
Here is some code you can use to have an working example:
select col1, cast(rowcol as row(col1 integer, col2 integer, col3 integer))
from (
values
(1, row(2,null,4)),
(1, row(null,3,null)),
(2, row(7,8,null)),
(2, row(null,null,56)),
(3, row(1,3,7))
)
AS x (col1, rowcol)
I am expecting the result as following:
|col1|rowcol |
|----|-------------------------------|
|1 |{col1=2, col2=3, col3=4} |
|2 |{col1=7, col2=8, col3=56} |
|3 |{col1=1, col2=3, col3=7} |
Maybe someone can help me...
Thanks in advance

Answer 1

You need to group them by col1 and process to merge not nulls, for example using max:
-- sample data
WITH dataset (col1, rowcol) AS (
VALUES
(1, row(2,null,4)),
(1, row(null,3,null)),
(2, row(7,8,null)),
(2, row(null,null,56)),
(3, row(1,3,7))
)
--query
select col1,
cast(row(max(r.col1), max(r.col2), max(r.col3)) as row(col1 integer, col2 integer, col3 integer)) rowcol
from (
select col1,
cast(rowcol as row(col1 integer, col2 integer, col3 integer)) r
from dataset
)
group by col1
order by col1 -- for ordered output
Output:
col1
rowcol
1
{col1=2, col2=3, col3=4}
2
{col1=7, col2=8, col3=56}
3
{col1=1, col2=3, col3=7}