Is there a way to simply do a left outer join using rails ActiveRecord?
I see here there are some ways using raw SQL, but I'd like to use the 'rails way' (presuming there is a rails way)
ie a query to retrieve the records represented by the maroon area:
Why not use raw SQL (like here ) - that's a fair question. My app has no raw sql, only syntax of the form customer.purchases
so I'd like to keep the code consistence across the app.
Rails >= 5 appears to have this capability built in.
Here 'sa simple example:
User.left_outer_joins(:posts)
=> SELECT "users".* FROM "users" LEFT OUTER JOIN "posts" ON "posts"."user_id" = "users"."id"
Here 's another example:
Author.left_joins :posts, :comments
# Produces:
Author Load (0.1ms) SELECT "authors".* FROM "authors" LEFT OUTER JOIN "posts" ON "posts"."author_id" = "authors"."id" LEFT OUTER JOIN "comments" ON "comments"."author_id" = "authors"."id"
This example from RailsGuides is also handy to know (although it contains some raw SQL):
Customer.left_outer_joins(:reviews).distinct.select('customers.*, COUNT(reviews.*) AS reviews_count').group('customers.id')
#Produces:
SELECT DISTINCT customers.*, COUNT(reviews.*) AS reviews_count FROM customers
LEFT OUTER JOIN reviews ON reviews.customer_id = customers.id GROUP BY customers.id
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