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Asked: 2026-05-22T23:09:47+00:00

I’ve just created my first mySQL table on my own (other than using Joomla,

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I’ve just created my first mySQL table on my own (other than using Joomla, WordPress, etc.) and I am MS SQL developer for years but normally I can easily create a foreign key in MS SQL but I came across a difficulty or lack of knowledge here.

Here is my tables :

users

  1. user_id int primary auto_increment
  2. username varchar(20)
  3. password varchar(20)

posts

  1. post_id in primary auto_increment
  2. title varchar(100)
  3. message text
  4. user_id int

When I try to add a foreign key to users which refers to posts->user_id, I cannot see the posts->user_id option in the option list Relation_view window on mySQL panel.

I am wondering whether I should define posts->user_id as Index or something? If so, why?

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1 Answer

  1. Editorial Team

    Short answer: Yes, MySQL forces you to index foreign key.

    InnoDB requires indexes on foreign keys and referenced keys so that foreign key checks can be fast and not require a table scan.

    You can read more about foreign keys on MySQL documentation pages: http://dev.mysql.com/doc/refman/5.5/en/innodb-foreign-key-constraints.html

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