railsのfindメソッドのincludeオプションとjoinsオプションの違いに付いてまとめてみた 環境 rails 1.2.3 DB構成 mysql> DESCRIBE users; +-------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+----------------+ | id | int(11) | | PRI | NULL | auto_increment | | name | varchar(40) | YES | | | | +-------+-------------+------+-----+---------