CODEWITHSUNDEEP
ruby-on-railsrubyactiverecord
tokhi
tokhi

Reputation: 21618

Get the User of an Object in one query

I have an Article model which is belongs_to a user so here I'm finding the user of a specific article as below:

article = Article.find(params[:id])
user = User.find(article.user_id)

As you see I achieve this via two queries, but I just want to have this in one single query. What you recommend? tnx.

Upvotes: 0

Views: 120

Answers (4)

flyingjamus
flyingjamus

Reputation: 4023

How about a join?

user = User.joins(:articles).where(articles: {id: params[:id]}).first

Upvotes: 1

Martin M
Martin M

Reputation: 8638

Sorry: as long as you want two objects, there is no way in Rails to select the data with one query.

You could construct a query that selects data of Article and User at the same time, store the user specific data in non DB attributes of Article like 

article = Article.where(id: params[:id]).joins(:user).select('articles.title, users.name').first
puts article.attributes['name']

that select all data in one query, but that really spoils Rails. You won't get an User instance.

Upvotes: 1

Sachin Singh
Sachin Singh

Reputation: 7225

try this out:-

article = Article.includes(:user).where("articles.id = ?",  params[:id]).first

now you can access user like article.user and no other query will get triggered.

this is known as eager loading:-

read more about it on rails guide.

http://guides.rubyonrails.org/active_record_querying.html#eager-loading-associations

see also:

http://railscasts.com/episodes/22-eager-loading
http://railscasts.com/episodes/22-eager-loading-revised

Upvotes: 0

Salil
Salil

Reputation: 47482

article = Article.includes(:user).where(:id => params[:id]).first

Upvotes: 2

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