From c7abc516f8fd7ccc4ae2bb528404ffb8a46ba4ba Mon Sep 17 00:00:00 2001 From: Yves Senn Date: Tue, 4 Feb 2014 13:37:11 +0100 Subject: [PATCH] docs, link MySQL manual for multi column indexes. [ci ckip]. Closes #9131. --- guides/source/active_record_validations.md | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/guides/source/active_record_validations.md b/guides/source/active_record_validations.md index b04c7a90e2..0ea2b86bb4 100644 --- a/guides/source/active_record_validations.md +++ b/guides/source/active_record_validations.md @@ -575,7 +575,9 @@ This helper validates that the attribute's value is unique right before the object gets saved. It does not create a uniqueness constraint in the database, so it may happen that two different database connections create two records with the same value for a column that you intend to be unique. To avoid that, -you must create a unique index in your database. +you must create a unique index on both columns in your database. See +[the MySQL manual](http://dev.mysql.com/doc/refman/5.6/en/multiple-column-indexes.html) +for more details about multi column indexes. ```ruby class Account < ActiveRecord::Base