Using Complex IF Statement in Oracle SQL

Question

Hi i\'m trying to write If statement in Band Attribute but without Success T_T. what Im trying to do is have single Character A, B, C, D depending on the owner_category, Sheds a

Answer 1

Read the documentation on virtual columns:

CREATE TABLE Rent_Band
(
    Plot_ID NUMBER(3),
    Band VARCHAR(1) AS
       (CASE WHEN Owner_Category = 'Council' AND Sheds ='No' THEN 'A'
            WHEN Owner_Category = 'Private' AND Water_Supply ='Yes' THEN 'D'
            WHEN Owner_Category = 'Council' AND Water_Supply ='No' AND Sheds ='Yes' THEN 'B'
            WHEN Owner_Category = 'Private' AND Water_Supply ='No' AND Sheds ='No' THEN 'B'
       ELSE 'C' END),
    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'))
)

BTW, I would STRONGLY recommend:

• using a bit field instead of a Yes/No constraint for Sheds and Water_Supply (saves room and overhead checking constraints, and translates directly to boolean in most app languages)
• using a lookup table for Owner_Category instead of a string constraint for basically the same reasons