Group list of dates based on values from joined table - sql

Question

DB-Fiddle
CREATE TABLE sales (
id SERIAL PRIMARY KEY,
event_date DATE,
country VARCHAR,
channel VARCHAR,
sales DECIMAL
);
INSERT INTO sales
(event_date, country, channel, sales)
VALUES
('2020-01-04', 'DE', 'channel_01', '500'),
('2020-01-04', 'FR', 'channel_01', '900'),
('2020-01-04', 'NL', 'channel_01', '100'),
('2020-02-20', 'DE', 'channel_01', '0'),
('2020-02-20', 'FR', 'channel_01', '0'),
('2020-02-20', 'NL', 'channel_01', '0'),
('2020-03-15', 'DE', 'channel_01', '700'),
('2020-03-15', 'FR', 'channel_01', '500'),
('2020-03-15', 'NL', 'channel_03', '300');
/* Table Dates */
CREATE TABLE dates (
id SERIAL PRIMARY KEY,
date DATE
);
INSERT INTO dates
(date)
SELECT generate_series ('2020-01-01'::date, '2020-12-31'::date, interval '1 day');
Expected Result:
date_list | country
--------------|--------------------------
2020-01-01 | DE
2020-01-01 | FR
2020-01-01 | NL
--------------|---------------------------
2020-01-02 | DE
2020-01-02 | FR
2020-01-02 | NL
--------------|---------------------------
: | :
: | :
: | :
--------------|--------------------------
2020-12-29 | DE
2020-12-30 | NL
2020-12-31 | FR
I want to list all dates from table dates and group them by all countries that are available in table sales no matter if the date exist in both tables. So far I have developed this query:
SELECT
d.date AS date_list,
t2.country
FROM dates d
LEFT JOIN
(SELECT
s.event_date,
s.country,
s.sales
FROM sales s
GROUP BY 1,2,3
ORDER BY 1,2) t2 ON t2.event_date = d.date
GROUP BY 1,2
ORDER BY 1,2;
However, it only groups the results by country if the s.event_date matches the d.date.
How do I have to modify the query to get the expected result?

Answer 1

I am not sure, if I understand your requirements right, but seems it is about CROSS JOIN
SELECT D.DATE,X.COUNTRY
FROM DATES AS D
CROSS JOIN
(
SELECT DISTINCT COUNTRY FROM SALES
)X