One on One table relation - is it harmful to keep relation in both tables?

Posted by EBAGHAKI on Stack Overflow See other posts from Stack Overflow or by EBAGHAKI
Published on 2010-03-31T16:20:27Z Indexed on 2010/03/31 16:23 UTC
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sql

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mysql

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database

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database-design

I have 2 tables that their rows have one on one relation.. For you to understand the situation, suppose there is one table with user informations and there is another table that contains a very specific informations and each user can only link to one these specific kind of informations ( suppose second table as characters )

And that character can only assign to the user who grabs it, Is it against the rules of designing clean databases to hold the relation key in both tables?

User Table: user_id, name, age, character_id Character Table: character_id, shape, user_id

I have to do it for performance, how do you think about it?

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