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docs, link MySQL manual for multi column indexes. [ci ckip]. 

Closes #9131.
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Yves Senn 2014-02-04 13:37:11 +01:00
parent 702e0e1a6b
commit c7abc516f8
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4
guides/source/active_record_validations.md
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@ -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