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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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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, 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 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, 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 ```ruby
class Account < ActiveRecord::Base class Account < ActiveRecord::Base