the car speed is 240 the car has an airbag Here the first value is integer and the second value is boolean. Consider that I have this table structure feature (feature id feature name) car (car id, .... ) car_feature (car id, feature id, value). the value attribute might have different domains. How can I model this using postgres and using ANSI compliant design ? Regards Given “feature” and “car-feature” tables the presence of absence of an entry in “car-feature” will accomplish your desire for true/false - i.e., “the car has an airbag”. By abstracting just a little every “feature” can be boiled down to a label/ID and then the added to “feature” and associated via “car-feature”. In your example you could create a feature called “Top Speed – 240kph” If every car is going to have a particular “feature” and only the “value” matters you could considering adding a “car-properties” table: car_property (car id, top_speed, etc…) and populate the top_speed column with whatever value is applicable or leave it NULL if unknown or N/A. The relationship between “car” and “car_property” would be one-to-one (1-to-1) Dave J. |
