Is the definition for "Secondary Index" anything more specific than just "Any index that is not the primary index"?

EDIT: Here is some research I have done:

  1. Search Google. I evaluated the first 20 results. These included:

    a) links to websites for priopetary DB products such as DynamoDB, Oracle, MySQL, etc. (and therefore not valid answers IMO because I'm asking about definitions independent of DB product)

    b) the opinion of someone named Devang Savaliya[1] who identifies as a Footballista and whose expertise I'm less than 100% confident in.

    c) Course notes from universities such as Simon Fraser University[2] and UC Davis[3], which don't seem to be specifically about database indices

    d) A defintion from TutorialsPoint.com[4]

  2. Refer to the Wikipedia entry for database indexes[5] which does not contain the word "secondary"

[1] https://www.quora.com/What-is-difference-between-primary-index-and-secondary-index-exactly-And-whats-advantage-of-one-over-another/answer/Devang-Savaliya [2] http://www.cs.sfu.ca/CourseCentral/354/zaiane/material/notes/Chapter11/node8.html [3] http://web.cs.ucdavis.edu/~green/courses/ecs165a-w11/7-indexes.pdf [4] http://www.tutorialspoint.com/dbms/dbms_indexing.htm [5] https://en.wikipedia.org/wiki/Database_index

  • That's a lot of research for just one term. Are you sure that a rigorous definition is this important? Jan 14, 2016 at 0:28
  • 1
    I think @RobertHarvey is saying is that sometimes (more often that we'd like) terms don't have exactly 1 accepted definition. That's just how it is sometimes, but it's nothing to stress yourself out over. If context alone isn't enough to infer the meaning you can always ask for clarification. So, maybe you shouldn't be working so hard to find this definition. You'll be able to cope without it :)
    – MetaFight
    Jan 14, 2016 at 2:24

1 Answer 1


Usually a 'secondary index' is an index which is not used to enforce the primary key constraint. This seems to be a pretty widely-accepted term in the world of relational DBMSes.

In non-relational world, I don't know.

Not the answer you're looking for? Browse other questions tagged or ask your own question.