Oi, eu estou tentando escrever If declaração no atributo da banda, mas sem sucesso T_T. o que estou tentando fazer é ter um único caractere A, B, C, D, dependendo do atributo owner_category, Sheds e Water_Supply. Qualquer ajuda será ótima ^^.

CREATE TABLE Rent_Band
(
    Plot_ID NUMBER(3),
    Band VARCHAR(1)
    IF SELECT * FROM Rent_Band WHERE Owner_Category = 'Council' AND WHERE Sheds ='No' THEN Band ='A'
    ELSE IF SELECT * FROM Rent_Band WHERE Owner_Category = 'Private' AND WHERE  Water_Supply ='Yes' THEN Band ='D'
    ELSE IF SELECT * FROM Rent_Band WHERE Owner_Category = 'Council' AND WHERE  Water_Supply ='No' AND WHERE Sheds ='Yes' THEN Band ='B'
    ELSE IF SELECT * FROM Rent_Band WHERE Owner_Category = 'Private' AND WHERE Water_Supply ='No' AND WHERE Sheds ='No' THEN Band ='B'
    ELSE THEN Band = 'C',
    Rent_Charge NUMBER(4), 
    Owner_Category VARCHAR(10) CONSTRAINT Checking_Owner_Category CHECK((Owner_Category='Private') OR (Owner_Category='Council')), 
    Sheds VARCHAR(3) CHECK((Sheds='Yes') OR (Sheds='No')), 
    Water_Supply VARCHAR(3) CHECK((Water_Supply='Yes') OR (Water_Supply='No'))
)