SQL query to get info from different tables - sql

Question

Need a help with sql query.
I have 2 tables.
Matches.
first_referee_arbitr_id
second_referee_arbitr_id
home_team
guest_team
date
Arbitrs.
id
name
surname
first_referee_arbitr_id and second_referee_arbitr_id are from Arbitrs table(id).
As the result I need to count how much each referee has been included in matches:
referee_first_count | referee_second_count | Arbitr Surname | Arbitr Name
My query now:
SELECT T1.referee_first_count, T2.referee_second_count, T1.surname, T1.name
FROM (
select matches.first_referee_arbitr_id, q.surname, q.name, count(*) AS referee_first_count
FROM matches
JOIN (
SELECT name, surname, id
FROM arbitrs
) as q ON matches.first_referee_arbitr_id=q.id
GROUP BY matches.first_referee_arbitr_id, q.name, q.surname
ORDER BY referee_first_count DESC
) T1 FULL OUTER JOIN
(
select matches.second_referee_arbitr_id, arbitr.surname, arbitr.name, count(*) AS referee_second_count
FROM matches
JOIN (
SELECT name, surname, id
FROM arbitrs
) as arbitr ON matches.second_referee_arbitr_id=arbitr.id
GROUP BY matches.second_referee_arbitr_id, arbitr.name, arbitr.surname
ORDER BY referee_second_count DESC
) T2
ON (
(T1.name = T2.name) AND (T1.surname = T2.surname)
)
Example
Arbitrs:
id | Name | Surname
1 John Rambler
2 Steve Crystler
3 Tom Ferguson
Matches:
first_referee_arbitr_id| second_referee_arbitr_id| home_team | guest_team | date
1 Chelsea Everton 22.06.2020
2 1 Liverpool Lester 28.06.2020
3 Dinamo K Dinamo M 06.07.2020
1 2 Juventus Dinamo K 10.10.2020
3 Dinamo K Chelsea 20.20.2020
Result:
referee_first_count | referee_second_count | surname | name
2 1 Rambler John
1 1 Crystler Steve
2 0 Ferguson Tom
My result now with query above:
referee_first_count | referee_second_count | surname | name
2 1 Rambler John
1 1 Crystler Steve
2 NULL NULL NULL

Answer 1

First aggregate the matches table (twice) and left join this to the Arbitrs table:
SELECT a.name , a.Surname , ISNULL(fir.first_count,0) , ISNULL( sec.sec_count,0)
FROM Arbitrs a
LEFT JOIN (
SELECT first_referee_arbitr_id,COUNT(*) as first_count
FROM Matches
GROUP BY first_referee_arbitr_id
) fir
ON fir.first_referee_arbitr_id = a.id
LEFT JOIN (
SELECT second_referee_arbitr_id,COUNT(*) as sec_count
FROM Matches
GROUP BY second_referee_arbitr_id
) sec
ON sec.second_referee_arbitr_id = a.id

Answer 2

SELECT
a.name
, a.surname
, COUNT(CASE WHEN m1.id IS NOT NULL THEN 1 end) referee_first_count
, COUNT(CASE WHEN m2.id IS NOT NULL THEN 1 end) referee_second_count
FROM
Arbitrs a
LEFT JOIN macthes m1
ON a.id = m.first_referee_arbitr_id
LEFT JOIN macthes m2
ON a2.id = m.second_referee_arbitr_id
GROUP BY
a.name
, a.surname
-- if you want to show only those with refrence
HAVING referee_first_count > 0 or referee_second_count > 0