逆水行舟不进则退，学无先后达者为先。

[url][b]http://guides.rails.info/active_record_querying.html[/b][/url] [size=medium][color=red][b]1 Retrieving Objects from the Database[/b][/color][/size] [color=red][b]1.1 Retrieving a Single Obje...