Postgres 11

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CREATE TABLE table1 (
    region text,
    surface int,
    decision boolean
);

INSERT INTO table1 VALUES
('A', 1, true),
('A', 5, false),
('A', 6, false),
('B', 10, true),
('B', 20, true),
('B', 100, false),
('B', 200, false);

SELECT * FROM table1;

CREATE TABLE



INSERT 0 7




region
surface
decision


A
1
t

A
5
f

A
6
f

B
10
t

B
20
t

B
100
f

B
200
f



SELECT 7


SELECT
    region,
    AVG(surface) FILTER (WHERE decision = true),
    AVG(surface) FILTER (WHERE decision = false)
FROM
    table1
GROUP BY region


region
avg
avg


B
15.0000000000000000
150.0000000000000000

A
1.00000000000000000000
5.5000000000000000



SELECT 2


SELECT
    region,
    AVG(CASE WHEN decision = true THEN surface END),
    AVG(CASE WHEN decision = false THEN surface END)
FROM
    table1
GROUP BY region


region
avg
avg


B
15.0000000000000000
150.0000000000000000

A
1.00000000000000000000
5.5000000000000000



SELECT 2

region	avg	avg
B	15.0000000000000000	150.0000000000000000
A	1.00000000000000000000	5.5000000000000000