Не съм много сигурен какъв е проблемът тук... Вероятно бих създал четири таблици:
-- a table of item types (t-shirt, birthday card, etc.)
CREATE TABLE ItemTypes (
TypeID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
TypeName VARCHAR(20) NOT NULL
);
-- a table of associated properties
CREATE TABLE TypeProperties (
PropertyID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
TypeID INT NOT NULL,
PropName VARCHAR(20) NOT NULL,
INDEX(Property, TypeID),
FOREIGN KEY(TypeID) REFERENCES ItemTypes(TypeID)
);
-- a table of specific items (XL Blue t-shirt, large bday card w/sports car, etc.)
CREATE TABLE Items (
ItemID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
TypeID INT NOT NULL,
ItemName VARCHAR(100) NOT NULL,
ItemPrice DECIMAL UNSIGNED NOT NULL,
ItemStock INT UNSIGNED NOT NULL,
INDEX(ItemID, TypeID),
FOREIGN KEY(TypeID) REFERENCES ItemTypes(TypeID)
);
-- the dictionary of property values
CREATE TABLE ItemProperties (
ItemID INT NOT NULL,
TypeID INT NOT NULL,
PropertyID INT NOT NULL,
Value VARCHAR(20) NOT NULL,
PRIMARY KEY(ItemID, Property),
INDEX(ItemID, TypeID),
INDEX(PropertyID, TypeID),
FOREIGN KEY( TypeID) REFERENCES ItemTypes ( TypeID),
FOREIGN KEY(ItemID, TypeID) REFERENCES Items (ItemID, TypeID),
FOREIGN KEY(PropertyID, TypeID) REFERENCES TypeProperties(PropertyID, TypeID)
);
Би трябвало да е доста очевидно, но за всеки случай примерните данни ще изглеждат така:
INSERT INTO ItemTypes (TypeID, TypeName) VALUES
(1, 'T-Shirt' ),
(2, 'Birthday Card'),
(3, 'Balloon' );
INSERT INTO TypeProperties(PropertyID, TypeID, PropName) VALUES
(51, 1, 'Colour' ), (52, 1, 'Size'),
(53, 2, 'Size/mm'), (54, 2, 'Size'), (55, 2, 'Design'),
(56, 3, 'Colour' );
INSERT INTO Items (ItemID, TypeID, ItemName, ItemPrice, ItemStock) VALUES
(101, 1, 'Extra Large Blue T-Shirt', 10.99, 20),
(102, 2, '6mm Large Birthday Card with Sports Car Design', 2.99, 17),
(103, 1, 'Extra Large Black T-Shirt', 10.99, 5),
(104, 3, 'Pink balloon', 0.10, 60);
INSERT INTO ItemProperties (ItemID, TypeID, PropertyID, Value) VALUES
(101, 1, 51, 'Blue' ),
(101, 1, 52, 'Extra Large'),
(102, 2, 53, '6' ),
(102, 2, 54, 'Large' ),
(102, 2, 55, 'Sports Car' ),
(103, 1, 51, 'Black' ),
(103, 1, 52, 'Extra Large'),
(104, 3, 56, 'Pink' );