Plusieurs conditions SQL dans deux tables renvoient des données erronées

Question

J'ai deux tables MySql avec le schéma suivant

Courses(CNO:CHAR(10),CName:VARCHAR(50), DeptId:CHAR(3)): Each course is given a
unique ID called CNO
Register(RNO:CHAR(10), CNO:CHAR(10), Year:INTEGER, Sem:INTEGER, Grade:CHAR)

Maintenant je dois trouver tous les triples (RNO, année, Sem) pour que l'étudiant ait le numéro de rôle RNO au semestre Tel que défini par année, Sem a suivi/s'est inscrit à au moins trois cours différents ou plus, chacun proposé par un département différent.

Mon code est le suivant

With tmp AS(
    SELECT Register.RNO,Register.CNO,Register.Year,Register.Sem,courses.DeptId, ROW_NUMBER() 
    OVER (PARTITION BY DeptId) 
    AS rn 
    from Register 
    inner join courses 
    on courses.CNO=Register.CNO
)
select RNO, Year, Sem
from tmp
where rn=1
GROUP BY RNO,Year,Sem 
having COUNT(CNO)>=3;

(J'ai utilisé Row_Number pour appliquer le mot-clé Distinct sur l'une des colonnes) Cependant, ce code échoue si l'étudiant est inscrit à plus de trois cours dans deux semestres différents et que le résultat est 1 ligne au lieu de 2 lignes. Pourquoi cela se produit-il et comment y remédier

Voici le code SQL pour les exemples de données et le schéma

CREATE TABLE courses (
    CNO CHAR(10),
    CName VARCHAR(50),
    DeptId CHAR(3),
    PRIMARY KEY (CNO)
);



INSERT INTO courses (CNO,CName,DeptId)
VALUES ("CS1","database","CSE");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("CS2","deep","CSE");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("CS3","prob","CSE");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("MBA4","consume","IME");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("MBA5","Model","IME");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("MBA7","consume","IME");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("MBA8","Model","IME");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("SOC6","Social","HSS");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("MBA10","consume","IME");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("MBA11","Model","IME");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("SOC12","Social","HSS");
INSERT INTO courses (CNO,CName,DeptId)
VALUES ("SOC9","Social","HSS");

CREATE TABLE Register (
    RNO CHAR(10),
    CNO CHAR(10), 
    Year INTEGER, 
    Sem INTEGER,
    Grade CHAR,
    FOREIGN KEY (CNO) REFERENCES courses(CNO)
);    

INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","CS1",1,1,"B");
INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","CS2",1,1,"A");
INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","CS3",1,1,"B");
INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","MBA4",1,1,"B");
INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","MBA5",1,1,"A");
INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","SOC6",1,1,"A");

INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","MBA7",2,2,"B");
INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","MBA8",2,2,"A");
INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","SOC9",2,2,"A");

INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","MBA10",3,3,"B");
INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","MBA11",4,3,"A");
INSERT INTO Register (RNO,CNO,Year,Sem,Grade)
VALUES ("1","SOC12",5,3,"A");

Voici le lien vers DB Fiddle.

Answer 1

Si j'ai bien deviné

select Register.RNO, Register.Year, Register.Sem 
from Register 
inner join courses on courses.CNO=Register.CNO
group by RNO,Year,Sem 
having COUNT(distinct courses.CNO)>=3 and COUNT(distinct courses.DeptId) >=3;