Home/ Questions/Q 9204411
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-17T23:42:21+00:00

I have a table like this: something a [INT] b [INT] c [INT] …where

  • 0

I have a table like this:

something
a [INT]
b [INT]
c [INT]

…where a, b and c are separate Foreign Keys pointing to three different table.id. Since I want to make all regs be unique, and after having read this great answer, I think I should create a new Index this way: UNIQUE INDEX(a, b, c) and (in my case) do IGNORE INSERTS.

But as you can see, I would have one KEY for each column and then another extra UNIQUE INDEX containing all three. Is this a normal thing? It seems strange to me, and I have never seen it.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    It is perfectly normal and reasonable to include a column in more than one index. However, if the combination of (a, b, c) is enough to uniquely identify a row it seems that you want a PRIMARY index instead of a UNIQUE one here (technically there is very little difference, but semantically it might be the better choice).

    • 0