changing an active record query from SQL query

Question

My SQL is alittle bit rusty but ive managed to get this piece of sql that works...

Select project_id, taskType, user_id, SUM(hours) 
From project_tasks, efforts
where project_tasks.id = efforts.project_task_id and project_tasks.project_id = 2 and project_tasks.taskType = "Pre-Sales"
group by user_id

what i want know is to transfer this sql statement into something that can be used in ruby on rails. So an active record query that can be referenced, probably along the lines of ..

@records = Effort.find(:all, :select => etc...

the problem is i cant seem to the work out how this can be done as i am new to ruby on rails.

Update

class Effort < ActiveRecord::Base
  belongs_to :project_task
  belongs_to :project
  belongs_to :user
end

class ProjectTask < ActiveRecord::Base
  belongs_to :project
  has_many :efforts
end

Answer 1

I'm assuming you're using Ruby on Rails 3 since this question is tagged with it, so here's the syntax:

 Effort.select('project_id, taskType, user_id, SUM(hours)')
       .joins(:project_task)
       .where(:project_tasks => {:project_id => 2, :taskType => 'Pre-Sales'})
       .group('user_id')

The major difference with my solution and your sql statement is that this will utilize a JOIN rather than just a condition between the two tables. You should also table prefix the column references to ensure no clashing occurs:

.group("#{Effort.quoted_table_name}.user_id")

This is untested so see if it acts as you'd expect.

Answer 2

If you want to implement your sql in rails with ActiveRecords, you could use scope

Ex:

class Effort < ActiveRecord::Base
  belongs_to :project_task
  belongs_to :project
  belongs_to :user

  scope :all_records, lambda { |project_id, task_type
    {
      :select => "project_id, taskType, user_id, SUM(hours) ",
      :from =>  "project_tasks, efforts",
      :where => "project_tasks.id = efforts.project_task_id and project_tasks.project_id =#{project_id} and project_tasks.taskType = '#{task_type}'",
      :group => "user_id" 
    }
  }

end

@records = Effort.all_records(2,"Pre-Sales")

I haven't tried this personally but should work

HTH

sameera