What do indexes look like in an Entity Relationship Diagram?

I've googled it and I'm unsure what the standard look of an index is in an ERD. And I'm talking about the crowsfoot diagram that includes all of the fields.

  • Why do you want to show indexes on ERD? Most tools provide a physical view of the model where you can denote and name indexes, but not on the ERD diagram itself.
    – NoChance
    Sep 4, 2012 at 6:37

1 Answer 1


They don't tend to be shown in ERDs. An ERD focuses on the Entities and their Relationships, but an index is a copy of the data from one (or potentially more) of the entities, created to assist in the execution of queries. While it's possible that an index could be unique and therefore contribute to the database design, they are not typically shown on ERDs.

...which is a shame, because in my experience, a database design should involve careful acknowledgement of the indexes, as they can make-or-break the effectiveness of a database system.

  • 3
    this is not a shame but it is not the intention of the entity relationship diagram to document physical implementation but to provide a conceptual model. The entity relationship diagram (usually with additional information) can be used to develop a physical implementation.
    – miracle173
    Sep 4, 2012 at 6:34
  • Sure. But there is no diagrammatic standard for indexes (so much as I'm aware) - and that's a shame.
    – Rob Farley
    Sep 4, 2012 at 7:05
  • 2
    While there is no standard the CA Associates ERwin tool does enable indexes to be shown using the words "IEx.y" or "AKx.y" where x is the index number and y is this columns position in that index. That convention is helpful to query writers when using the ERD to help them navigate the database for joins. I hope this helps. Sep 4, 2012 at 21:44

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