n350071🇯🇵

Posted on Jan 29, 2020 • Updated on Mar 1, 2022

rails query

#rails

First of all, Scope is same as Class method

def self.with_suger
  where("suger > 0")    
end

This is same as

scope :with_suger, -> {
  where("suger > 0")    
}

and then, use it as class method.

BendingMachine.with_suger

cut in

I'd recommend you to use this, otherwise, you will see this error message when you join and merge the scope with another model scope.
Especially, when your model name and table name is different, you easily go into confusing. But this way, you'll be still in Object World.

ActiveRecord::StatementInvalid:
  Mysql2::Error: Column 'created_at' in where clause is ambiguous:

scope :created_until_the_day, -> (date) {
  where("#{table_name}.created_at < ?",  date)
}

scope :creator_filter, -> {
  where(creator: true)
}

scope :over_x_years_old, (x)-> {
  where('age >= ?', x)
}

It makes "Inner Join" on with the relation.

scope :with_authored_book, -> {
  joins(:book)
}

scope :with_authored_book_and_laptop, -> {
  joins(:book, :laptop)
}

scope :with_authored_book_of_abc_publisher, -> {
  joins(book: :publisher)
}

scope :with_authored_book_of_abc_publisher, -> {
  joins(:laptop, {book: :publisher})
}

You can write both ways.

.where(User.table_name => {name: 'john connor'})
.where("#{User.table_name}.name = ?", 'john connor')

joins(:user)
.where("#{User.table_name}.name = ?", 'john connor')

joins(:user)
.where(User.table_name => {name: 'john connor'})

joins(:user)
.merge(User.where(name: 'john connor'))

WHERE NOT exists (
  SELECT *
  FROM users
  WHERE users.company_id = :company_id
    AND users.story_id = stories.id
)

.where(User.joins(:company, :story).where(comapny_id: company_id).exists.not)