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Editorial Team
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Asked: 2026-05-16T06:48:10+00:00

I’m currently working on a data model design (which will be backed by an

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I’m currently working on a data model design (which will be backed by an RDMS). It is based around 3 entities relating to benefits for a member of the organization. The entities are the Benefit, Membership Type, and Provider. I’ve created a standard many-to-many intersection table to relate two entities, but never 3. I’m wondering if anybody has done such a thing and if there are any potential pitfalls I should keep out for. The table would be like the following:

create table BENEFIT_MEM_TYPE_PROVIDER
(
   BENEFIT_ID reference BENEFITS not null,
   MEMBERSHIP_TYPE_ID reference MEMBERSHIP_TYPES not null,
   PROVIDER_ID reference PROVIDERS not null,
   primary key (BENEFIT_ID, MEMBERSHIP_TYPE_ID, PROVIDER_ID)
)

Something about this relationship just doesn’t sit right with me, so I thought I’d ask the smart folks for any advice.

Thanks

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1 Answer

  1. Editorial Team

    Yes.

    Ternary relationships are quite widely used, although not as widely used as binary relationships. This can even be extended to quaternary or in general n-ary relationships.

    One place where you can see n-ary relationships in database design is star schema. The fact table at the center of a star is an n-ary relationship, where n is the number of dimension tables referenced by the fact table.

    The normalization process consists of detecting departures from some normal form, and decomposing tables in order to yield a more normalized equivalent. Decomposition sometimes results lowering the order of n-ary relationships.

    Star schema deliberately goes the other way. That is why star schema and normalization are so frequently seen as being at odds with each other.

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