Creating a query to structure results grouped by two columns, pivoting only a third colum

From: Iuri Sampaio <iuri(dot)sampaio(at)gmail(dot)com>
To: pgsql-sql(at)lists(dot)postgresql(dot)org
Subject: Creating a query to structure results grouped by two columns, pivoting only a third colum
Date: 2021-09-25 16:39:34
Message-ID: 4A8701B1-72AA-408F-9A7D-8DDC358E8AB3@gmail.com
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Hello there,
In order to achieve such structure "pivoting" table and "grouping by" multiple columns. (i.e. as illustrated below), what would be the SQL implementation?
The source query is:

````
SELECT
t1.date,
t1.area,
t1.canal,
SUM(t1.peso) AS peso
FROM table1 t1
GROUP BY 1, 2, 3
ORDER BY 1, 2, 3

````

and source query generates a initial structure as in:

###########################
date | area | canal | peso
2021-03-01 area1 can1 45.6768
2021-03-01 area1 can2 54.6768
2021-03-01 area1 can3 87.6
2021-03-01 area2 can1 1.87
2021-03-01 area2 can2 12.7687
2021-03-01 area2 can3 965.568
2021-03-01 area3 can1 968.95
2021-03-01 area3 can2 1.6867
2021-03-01 area3 can3 8.897
…. … … ...
2021-06-01 area1 can1
2021-06-01 area1 can2
2021-06-01 area1 can3
2021-06-01 area2 can1
… … ...

2021-12-01 area1
2021-12-01 area1
2021-12-01 area1
###########################

Then, the goal's to achieve a final structure grouped by columns "area" and "canal", pivoting column “date", but only to the column "peso".
Plus, a partial total of each area, named as "total” .

I tried to write a query to support such a display, however, I got stuck at pivoting date only to the column peso

````
SELECT
t2.area,
t2.canal,
( SELECT
month,
peso_valor
FROM (
SELECT
month(t1.date) month,
t1.area,
t1.canal,
SUM(t1.peso_valor) AS peso_valor
FROM tbl_data t1
GROUP BY 1, 2, 3
ORDER BY 1, 2, 3
) source_table
) PIVOT (
peso
FOR month IN (
1 Jan, 2 Feb, 3 Mar, 4 Apr, 5 Mai, 6 Jun, 7 Jul, 8 Aug, 9 Sep, 10 Oct, 11 Nov, 12 Dec
)
) as pivot_table
ORDER BY month
) as t2.peso
FROM tbl_data t2
GROUP BY 1, 2
````

what would be the SQL implementation to achieve a structure as such ?
(.i.e. grouped by columns "area" and "canal", pivoting column “date", but only to the column "peso”.)

illustrated bellow?

Best wishes,
I

###########################
area | canal | 2021-03-01 | 2021-04-01 | 2021-05-01 | 2021-06-01 | ...
peso peso peso peso

area1 can1 45.6768 875.98 1.232 …
area1 can2 54.6768 665.8 2.43 ...
area1 can3 87.6 65.8 4.76 ...
area1 total SUM(45.6768+54.6768+87.6) SUM(875.98+665.8+65.8) SUM(1.232+2.43+4.76) ...

area2 can1 1.87 … ...
area2 can2 12.7687
area2 can3 965.568
area2 total SUM(1.87+12.7687+965.568) … ...

area3 can1 968.95
area3 can2 1.6867
area3 can3 8.897

...
###########################

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