SQL: count and sum based on conditions from the related table - mysql

Question

I have two tables;
countries(id, name, region);
1, 'UK', '1';
2, 'USA', '1';
3, 'AUSTRALIA', '1';
4, 'CHINA', '0';
5, 'INDIA', '0';
6, 'SRI LANKA', '0' ;
and
tickets(id, country_id, issued_date, holder, gender, fee, canceled);
100, 2, 2017-08-15, 'Person 1', 'M', 200, '1';
101, 2, 2017-08-15, 'Person 2', 'M', 200, '0';
103, 3, 2017-08-15, 'Person 3', 'M', 200, '0';
104, 5, 2017-08-16, 'Person 1', 'M', 200, '0';
105, 6, 2017-08-16, 'Person 1', 'M', 200, '0';
106, 1, 2017-08-17, 'Person 1', 'M', 200, '0';
107, 3, 2017-08-18, 'Person 1', 'M', 200, '1';
108, 4, 2017-08-18, 'Person 1', 'M', 200, '0';
I want to group all the tickets based on issued_date with some aggregates fields to generate the summary. Here is my query:-
SELECT
issued_date,
COUNT(*) as total_tickets,
COUNT(CASE WHEN canceled = '0' THEN 1 ELSE NULL END) as issued_tickets,
SUM(CASE WHEN canceled = '0' THEN fee ELSE NULL END) as total_amount
FROM tickets
GROUP BY issued_date;
But, how to use COUNT and SUM for related table countries? For example, I want to show how many tickets were sold on a date (2017-08-15) from a country having region = '1'.
I tried the following, but the results are not correct for region_1 field
SELECT
issued_date,
COUNT(*) as total_tickets,
COUNT(CASE WHEN canceled = '0' THEN 1 ELSE NULL END) as issued_tickets,SUM(CASE WHEN canceled = '0' THEN fee ELSE NULL END) as total_amount,
(SELECT COUNT(countries.id) FROM countries WHERE countries.id = tickets.country_id && countries.region = '1') as region_1
FROM tickets
GROUP BY issued_date;

Answer 1

I would use a derived table that is grouped on issue_date, country_id and region and use that derived table in an inner join.
SELECT issued_date
,COUNT(*) AS total_tickets
,COUNT(CASE WHEN canceled = '0' THEN 1 ELSE NULL END) AS issued_tickets
,SUM(CASE WHEN canceled = '0' THEN fee ELSE NULL END) AS total_amount
,tickets_by_region.total_region_1_tickets
FROM tickets
INNER JOIN (
SELECT issued_date
,country_id
,countries.region
,COUNT(*) AS total_region_1_tickets
FROM tickets
INNER JOIN countries ON (countries.id = tickets.country_id)
GROUP BY issued_date
,countries.country_id
,countries.region
) tickets_by_region ON (
tickets_by_region.issued_date = tickets.issued_date
AND tickets_by_region.country_id = tickets.country_id
AND tickets_by_region.region = '1'
) AS region_1
GROUP BY issued_date;
HTH.

Answer 2

You probably need to use INNER JOIN and GROUP BY with HAVING which allow append next table on related keys and add to additional summary or counts you need to use them like sub-query because they need to work with no filtered data.
Approach is prepare data in sub-query and then JOIN the filtered data
to your main table which can do final filtering for final result.
SQL can looks like bellow (tested on local)
SELECT t1.issued_date, COUNT(t1.id) as sum_tickets, t2.region, t3.total_tickets
FROM tickets t1
LEFT JOIN (SELECT id, COUNT(id) as total_tickets FROM tickets) t3 ON t3.id = t1.id
INNER JOIN countries t2 ON t2.id = t1.country_id
GROUP BY t1.issued_date
HAVING (t2.region = '1')
Output is
issued_date, sum_tickets, region, total_tickets
2017-08-15, 3, 1, 8
2017-08-17, 1, 1, null
2017-08-18, 2, 1, null
You can add more conditions to HAVING in query.

Answer 3

I would just use conditional aggregation with a JOIN:
SELECT t.issued_date, COUNT(*) as total_tickets,
SUM(t.canceled = 0) as issued_tickets,
SUM(CASE WHEN t.canceled = 0 THEN t.fee END) as total_amount,
SUM(c.region = 1) as num_region_1
FROM tickets t JOIN
countries c
ON t.country_id = c.id
GROUP BY t.issued_date;