Ruby on Rails MySQL搜索

Question

I am totally new to Ruby on Rails and I am trying to search through some relational database tables, I am trying to search for a given ID number in a Customer table then from the results look at who the sales_rep for that customer is. With this

@salesrepcust = Customer.find(:all, :conditions => ["id = ?",@data])

I am able to get back the correct customer given there ID number but I dont see how in ruby on rails to then pull from those results just one column value, in this it would be the value for sales_rep, and then use that as my @result for

@salesrepcustdata = Salesrep.find(:all, :conditions => ["id = ?", @result])

I have searched for this but i guess im not wording it correctly because i am not able to find anything specifically on this, can anyone help?

Answer 1

Assuming the sales rep is represented in the Customer table as sales_rep_id you can just do:

Salesrep.find(Customer.find(@data).sales_rep_id)

The find method assumes you're looking for id and if there's just one item with that id , there's no need to specify :all .

This is all discussed in http://guides.rubyonrails.org/active_record_querying.html

Answer 2

That Customer query could be simplified to just:

@customer = Customer.find(@data)

You don't mention if you've setup a relationship between Customer and Salesrep but here goes:

# app/models/customer.rb
class Customer < ActiveRecord::Base
  belongs_to :salesrep, class_name: 'Salesrep' # => the customers table should have a salesrep_id column
end

# app/models/salesrep.rb
class Salesrep < ActiveRecord::Base
  has_many :customers
end

customer_id = 1
@customer = Customer.find(customer_id)
@salesrep = @customer.salesrep

# from the other way, assuming you need both the salesrep and customer:
salesrep_id = 10
@salesrep = Salesrep.find(salesrep_id)
# the following will only find the customer if it's owned by the Salesrep
@customer = @salesrep.customers.find(customer_id)

Answer 3

It's pretty straightforward to select a single column; you can try something like this:

@salesrepcustids = Customer.where(id: @data).select(:id)

This will generate a SELECT id FROM ... statement.

And now you can do this:

@salesrepcustdata = Salesrep.where(id: @salesrepcustids)

This will generate an SELECT...IN statement with those ids.

(You might find it easier to set up proper ActiveRecord has_many and belongs_to relationships in your models, or whatever relationship is appropriate.)