Question

I am new to ruby and have the following:

students = Student.all(:order => "score DESC",
            :limit => 5)

However I want to put a where clause into this as well but I get the error “Unknown key: where”. My student table references an exam table (t.references :exam) which has a date field so I need to do something like:

students = Student.all(:where => "exam.date='01/01/2012'",
                       :order => "score DESC",
                       :limit => 5)

How do I use a where clause in the all method and is exam.date='01/01/2012' correct ?

Answer 1

The all method with arguments is a pre-Rails 3 API, and all(*args) is equivalent to find(:all, *args), which takes the :conditions option:

students = Student.all(:conditions => "exam.date='01/01/2012'",
                       :order => "score DESC",
                       :limit => 5)

It is generally preferred to use Rails 3’s chain-able relation methods, though:

students = Student.where("exam.date='01/01/2012'").order('score DESC').limit(5)