Rails Query Multiple Params From Same Table - ruby-on-rails

Question

How can I search for multiple params? I have checkboxes in my view, so if multiple checkboxes are selected, I would like all the params selected to be chosen. I can currently only get the search to work with one param with code below.
There is a has_many to has_many association between car model and colour_collection model.
Controller:
#cars = car.joins(:colour_collections).where("colour_collections.name = ?", params[:colour_collection])
logs show this if two colours selected (e.g. red and green) creating duplicates in the resulting querie:
(0.7ms) SELECT COUNT(*) FROM "colour_collections"
ColourCollection Load (0.5ms) SELECT "colour_collections".* FROM "colour_collections"
Car Load (2.5ms) SELECT "cars".* FROM "cars" INNER JOIN "car_colour_collections" ON "car_colour_collections"."car_id" = "cars"."id" INNER JOIN "colour_collections" ON "colour_collections"."id" = "car_colour_collections"."colour_collection_id" WHERE "colour_collections"."name" IN ('Subtle', 'Intermediate') ORDER BY "cars"."created_at" DESC
CarAttachment Load (0.5ms) SELECT "car_attachments".* FROM "car_attachments" WHERE "car_attachments"."car_id" = $1 ORDER BY "car_attachments"."id" ASC LIMIT $2 [["car_id", 21], ["LIMIT", 1]]
CACHE (0.0ms) SELECT "car_attachments".* FROM "car_attachments" WHERE "car_attachments"."car_id" = $1 ORDER BY "car_attachments"."id" ASC LIMIT $2 [["car_id", 21], ["LIMIT", 1]]
CarAttachment Load (0.5ms) SELECT "car_attachments".* FROM "car_attachments" WHERE "car_attachments"."car_id" = $1 ORDER BY "car_attachments"."id" ASC LIMIT $2 [["car_id", 20], ["LIMIT", 1]]
CACHE (0.0ms) SELECT "car_attachments".* FROM "car_attachments" WHERE "car_attachments"."car_id" = $1 ORDER BY "car_attachments"."id" ASC LIMIT $2 [["car_id", 20], ["LIMIT", 1]]

Answer 1

If you want to search for multiple values in a single column for example
params[:colour_collection] = ['red','green','blue']
Then you would expect your query to look like this
SELECT * FROM cars c
INNER JOIN colour_collections s
WHERE s.name IN ('red','green','blue');
In this case the corresponding ActiveRecord statement would look like this
Car.
joins(:colour_collections).
where(colour_collections: { name: params[:colour_collection] })

Answer 2

Rails 5 comes with an or method but Rails 4 does not have the or method, so you can use plain SQL query in Rails 4.
In Rails 4 :
#cars = car.
joins(:colour_collections).
where("colour_collections.name = ? or colour_collections.type = ?", params[:colour_collection], params[:type])
In Rails 5 :
#cars = car.
joins(:colour_collections).
where("colour_collections.name = ?", params[:colour_collection]).or(car.joins(:colour_collections).where("colour_collections.type = ?", params[:type]))

Answer 3

Depending on whether you want to use OR or AND. There are multiple ways of achieving this but simple example is
Article.where(trashed: true).where(trashed: false)
the sql generated will be
SELECT * FROM articles WHERE 'trashed' = 1 AND 'trashed' = 0
Foo.where(foo: 'bar').or.where(bar: 'bar') This is norm in Rails 5 or simply
Foo.where('foo= ? OR bar= ?', 'bar', 'bar')

Answer 4

#cars = car.joins(:colour_collections).where("colour_collections.name = ?", params[:colour_collection]).where("cars.make = ?", params[:make])
More discussion on chaining How does Rails ActiveRecord chain "where" clauses without multiple queries?