如何仅查询特定列？

Question

典型情景：

SomeModule.find(:all, :conditions ["xyz" = ?, some_var]
SomeModule.find(:first, :conditions ["xyz" = ?, some_var]
SomeModule.find(:last, :conditions ["xyz" = ?, some_var]

Desired Equivilent：

虽然以上三个例子很棒，但我正在寻找正确的方法来询问“仅”特定列，例如：

SomeModule.find(:first_name, last_name, city :conditions ["xyz" = ?, some_var]

- 或许 - -

SomeModule.find(:only => :first_name, :last_name, :city :conditions ["xyz" = ?, some_var]

在查询中删除不必要的列的轨道方式是什么？

Answer 1

SomeModule.find(:select => "first_name, last_name, city" ... )

文档：ActiveRecord::QueryMethods