ruby-on-rails – find_by_id(params [：subject_id])vs where where(：id => params [：subject_id]).first

我是铁杆新手.只是想知道哪个是更好的方法,如果找不到subject_id,将返回nil：

@subject = Subject.find_by_id(params[:subject_id])

要么

@subject = Subject.where(:id => params[:subject_id]).first

谢谢.

解决方法

它们都生成相同的sql语句：

1.9.3p194 :003 > Example.find_by_id(9)
  Example Load (0.3ms)  SELECT "examples".* FROM "examples" WHERE "examples"."id" = 9 LIMIT 1
nil
1.9.3p194 :004 > Example.where(:id => 9).first
  Example Load (0.3ms)  SELECT "examples".* FROM "examples" WHERE "examples"."id" = 9 LIMIT 1
nil

因此,它们在数据库中具有相同的性能特征. find_by _ * _与where的Rails代码可能略有不同,但我认为与查询时间相比,这可以忽略不计.

编辑：鉴于Ryan Bigg’s comment below,我必须建议第二种形式的向前兼容性.