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Editorial Team
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Asked: 2026-05-12T09:08:33+00:00

Sorry for the bad title, but I have no idea how to put this

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Sorry for the bad title, but I have no idea how to put this in short. The Problem is the following:

I have a generic item that represents a group, lets call it Car. Now this Car has attributes, that range within certain limits, lets say for example speed is between 0 and 180 for a usual Car. Imagine some more attributes with ranges here, for example Color is between 0 and 255 whatever that value might stand for.

So in my table GenericItems I have:

ID    Name

 1    Car

And in my Attributes I have:

ID   Name   Min_Value    Max Value
 1   Speed     0            180
 2   Color     0            255

The relation between Car and Attributes is thus 1:n.

Now I start having very specific instances of my Car for example a FordMustang, A FerrariF40, and a DodgeViper.
These are specific instances and now I want to give them specific values for their attributes.

So in my table SpecificItem I have:

ID    Name           GenericItem_ID

 1    FordMustang         1
 2    DodgeViper          1
 3    FerrariF40          1

Now I need a third table SpecificAttributes2SpecificItems, to match attributes to SpecificItems:

ID    SpecificItem_ID   Attribute_ID   Value

 1         1                1           120        ;Ford Mustang goes 120 only
 2         1                2           123        ;Ford Mustang is red
 3         2                1           150        ;Dodge Viper goes 150
 4         2                2           255        ;Dodge Viper is white
 5         3                1           180        ;FerrariF40 goes 180
 6         3                2             0        ;FerrariF40 is black

The problem with this design is, as you can see, that I am basically always copying over all rows of attributes, and I feel like this is bad design, inconsistent etc. How can I achieve this logic in a correct, normalized way?

I want to be able to have multiple generic items, with multiple attributes with min/max values as interval, that can be “instantiated” with specific values

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1 Answer

  1. Editorial Team

    It looks like you’re trying to replicate Entity Atribute Value as a design, which leads to a lot of ugly tables (well, usually it is one single table for everything).

    http://en.wikipedia.org/wiki/Entity-attribute-value_model
    http://ycmi.med.yale.edu/nadkarni/Introduction%20to%20EAV%20systems.htm

    Discussing EAV tends to lead to “religious wars” as there are very few good places to use it (many folks say there are zero good places) and there are other folks who think that since it is so very flexible, it should be used everywhere. If I can find the reference I’m looking for, I’ll add it to this.

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