Using multiple foreign keys in a SQL select statement - sql

Question

I have four tables, one of them named matches and another one named teams. I need to display the teamCode in teams with the number of point they have that we can calculate in matches. Each win is 2 points each draw one point and each lost zero.
CREATE TABLE divisions
(
codediv CHAR(1) NOT NULL,
nomdiv VARCHAR2(40)
);
ALTER TABLE divisions
ADD CONSTRAINT divisions_pk PRIMARY KEY (codediv);
CREATE TABLE teams
(
teamCode CHAR(3) NOT NULL,
teamName VARCHAR2(50),
codediv CHAR(1) NOT NULL,
ville VARCHAR2(40),
nbcoupes NUMBER
);
ALTER TABLE teams ADD CHECK (nbcoupes >= 0);
ALTER TABLE teams ADD CONSTRAINT teams_pk PRIMARY KEY (teamCode);
CREATE TABLE joueurs
(
numjoueur NUMBER(3) NOT NULL,
nom VARCHAR2(30),
prenom VARCHAR2(30),
codeequipe CHAR(3)
);
ALTER TABLE joueurs ADD CONSTRAINT joueurs_pk PRIMARY KEY (numjoueur);
CREATE TABLE matchs
(
MatchNumber NUMBER(4) NOT NULL,
datematch DATE,
codeVisitingTeam CHAR(3) NOT NULL,
codeReceivingTeam CHAR(3) NOT NULL,
scoreVisitingTeam NUMBER(2),
scoreReceivingTeam NUMBER(2)
);
ALTER TABLE matchs ADD CONSTRAINT matchs_pk PRIMARY KEY (MatchNumber);
CREATE TABLE statistiques
(
nummatch NUMBER(4) NOT NULL,
numjoueur NUMBER(3) NOT NULL,
nbbuts NUMBER(3),
nbpasse NUMBER(3)
);
ALTER TABLE statistiques
ADD CONSTRAINT statistiques_pk PRIMARY KEY (numjoueur, nummatch);
ALTER TABLE matchs
ADD CONSTRAINT codeVisitingTeam FOREIGN KEY ( codeVisitingTeam)
REFERENCES teams ( teamCode );
ALTER TABLE teams
ADD CONSTRAINT teams_divisions_fk FOREIGN KEY ( codediv )
REFERENCES divisions ( codediv );
ALTER TABLE joueurs
ADD CONSTRAINT joueurs_equipes_fk FOREIGN KEY ( teamCode )
REFERENCES equipes ( teamCode );
ALTER TABLE matchs
ADD CONSTRAINT matchs_equipes_fk FOREIGN KEY ( CodeReceivingTeam )
REFERENCES equipes ( teamCode );
ALTER TABLE statistiques
ADD CONSTRAINT statistiques_joueurs_fk FOREIGN KEY ( numjoueur )
REFERENCES joueurs ( numjoueur );
ALTER TABLE statistiques
ADD CONSTRAINT statistiques_matchs_fk FOREIGN KEY ( nummatch )
REFERENCES matchs ( nummatch );
insert into divisions values('O', 'OUEST');
insert into divisions values('E', 'EST');
insert into equipes values('MTL', 'LES CANADIENS DE MONTRÉAl', 'E', 'MONTRÉAl', 24);
insert into equipes values('TOR', 'LES MAPLE LEAFS', 'E', 'TORONTO', 22);
insert into equipes values('OTT', 'LES SÉNATEURS', 'E', 'OTTAWA', 4);
insert into equipes values('AVL', 'LES AVALANCHES', 'O', 'COLORADO', 2);
insert into equipes values('VAN', 'LES CANUKS', 'O', 'VANCOUVER', 1);
insert into equipes values('BRU', 'LES BRUNS DE BOSTON', 'E', 'BOSTON', 13);
insert into Joueurs values(1, 'PRICE', 'CAREY', 'MTL');
insert into Joueurs values(2, 'MARKOV', 'ANDRÉ', 'MTL');
insert into Joueurs values(3, 'SUBBAN', 'KARL', 'MTL');
insert into Joueurs values(4, 'PATIORETTY', 'MAX', 'MTL');
insert into Joueurs values(10, 'HAMMOND', 'ANDREW', 'OTT');
insert into Joueurs values(6, 'STONE', 'MARC', 'OTT');
insert into Joueurs values(9, 'TURIS', 'KYLE', 'OTT');
insert into Joueurs values(7, 'GALLAGHER', 'BRANDON', 'MTL');
insert into Joueurs values(8, 'TANGUAY', 'ALEX', 'AVL');
insert into Joueurs values(11, 'THOMAS', 'BIL', 'AVL');
insert into Joueurs values(5, 'PATOCHE', 'ALAIN', NULL);
insert into Joueurs values(12, 'POIRIER', 'JUTEUX', NULL);
insert into Matchs values(100, TO_DATE('18-10-30', 'YY/MM/DD'), 'MTL', 'TOR', 3 , 4);
insert into Matchs values(101, TO_DATE('18-11-10', 'YY/MM/DD'), 'TOR', 'MTL', 3 , 3);
insert into Matchs values(102, TO_DATE('18-10-12', 'YY/MM/DD'), 'MTL', 'OTT', 2 , 0);
insert into Matchs values(103, TO_DATE('18-10-20', 'YY/MM/DD'), 'OTT', 'MTL', 0 , 1);
insert into Matchs values(104, TO_DATE('18-11-30', 'YY/MM/DD'), 'MTL', 'AVL', 3 , 4);
insert into Matchs values(105, TO_DATE('18-11-10', 'YY/MM/DD'), 'AVL', 'MTL', 0 , 0);
insert into Matchs values(106, TO_DATE('18-12-12', 'YY/MM/DD'), 'MTL', 'VAN', 2 , 0);
insert into Matchs values(107, TO_DATE('18-03-17', 'YY/MM/DD'), 'VAN', 'MTL', 3 , 1);
insert into Matchs values(108, TO_DATE('18-11-30', 'YY/MM/DD'), 'OTT', 'VAN', 0 , 0);
insert into Matchs values(109, TO_DATE('18-11-10', 'YY/MM/DD'), 'OTT', 'TOR', 0 , 4);
insert into Matchs values(114, TO_DATE('18-10-30', 'YY/MM/DD'), 'BRU', 'TOR', 3 , 4);
insert into Matchs values(115, TO_DATE('19-02-15', 'YY/MM/DD'), 'AVL', 'TOR', null , null);
insert into Matchs values(120, TO_DATE('18-02-26', 'YY/MM/DD'), 'MTL', 'AVL', null , null);
insert into Matchs values(121, TO_DATE('19-02-20', 'YY/MM/DD'), 'MTL', 'OTT', null , null);
Insert into statistiques values(100,3,2,2);
Insert into statistiques values(100,7,1,1);
Insert into statistiques values(101,3,1,0);
Insert into statistiques values(101,7,0,1);
Insert into statistiques values(101,4,1,2);
Insert into statistiques values(101,2,1,2);
Insert into statistiques values(100,4,0,2);
Insert into statistiques values(102,3,1,1);
Insert into statistiques values(102,7,1,2);
Insert into statistiques values(102,9,0,1);
Insert into statistiques values(106,4,1,1);
Insert into statistiques values(106,3,0,2);
Insert into statistiques values(106,2,1,0);
Insert into statistiques values(100,1,null,null);
Insert into statistiques values(101,1,null,null);
Insert into statistiques values(103,1,null,null);
Insert into statistiques values(102,1,null,null);
I've started with this to get the winning teams
select *
from
(select v.teamcode, count(m.codeVisitingTeam) as WonMatches
from matchs m
join teams v on v.teamCode = m.codeVisitingTeam
where m.scoreVisitingTeam > m.scoreReceivingTeam
group by v.teamCode
union all
select r.codeequipe, count(m.codeequiper) as WonMatches
from matchs m
join teams r on r.teamCode = m.codeReceivingTeam
where m.scoreReceivingTeam > m.scoreVisitingTeam
group by r.teamCode));
The only problem with the code above is that it returns twice the team 'MTL' as so :
VAN 1
MTL 2
AVL 1
TOR 3
MTL 1

Answer 1

So I was having a bit of fun with your query and did a bit more than you asked. I wrote the following query to calculated the full complement of wins, losses, and ties. I then ordered the results by points (3 points for a win and 1 for a draw). I hope this helps you a bit:
SELECT *
FROM (SELECT TeamCode,
CASE
WHEN (team = 'VISTING' AND scoreVisitingTeam > SCORERECEIVINGTEAM) OR (team = 'RECEIVING' AND SCORERECEIVINGTEAM > SCOREVISITINGTEAM) THEN 'WIN'
WHEN (team = 'VISTING' AND scoreVisitingTeam < SCORERECEIVINGTEAM) OR (team = 'RECEIVING' AND SCORERECEIVINGTEAM < SCOREVISITINGTEAM) THEN 'LOSS'
ELSE 'DRAW'
END AS RESULT
FROM matchs
UNPIVOT (TeamCode FOR Team IN (CodeVisitingTeam AS 'VISTING', CodeReceivingTeam AS 'RECEIVING')))
PIVOT(COUNT(*) FOR RESULT IN ('WIN' AS WINS, 'LOSS' AS LOSSES, 'DRAW' AS DRAWS))
ORDER BY (wins*3)+draws DESC;
If you have questions, please let me know.
I also created a SQLFiddle. (Link) Note: I removed your constraints from the SQLFiddle. They were throwing errors and I didn't feel like debugging it.

Answer 2

You can do it in a single query with conditional aggregation:
select e.teamCode,
sum(
case
when (e.teamCode = m.codeReceivingTeam and m.scoreReceivingTeam > m.scoreVisitingTeam)
or (e.teamCode = m.codeVisitingTeam and m.scoreReceivingTeam < m.scoreVisitingTeam) then 2
when m.scoreReceivingTeam = m.scoreVisitingTeam then 1
else 0
end
) total_points
from equipes e inner join matchs m
on e.teamCode in (m.codeReceivingTeam, m.codeVisitingTeam)
group by e.teamCode