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Diffstat (limited to 'guides')
| -rw-r--r-- | guides/source/active_record_validations.md | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/guides/source/active_record_validations.md b/guides/source/active_record_validations.md index efa826e8df..b0bd16791d 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 |