rails 4から導入された where.not

http://robots.thoughtbot.com/activerecords-wherenot

not equal系

# old
User.where.not(name: 'Gabe')`
User.where('name != ?', 'Gabe')

not null系

# Old and busted
# User.where('name IS NOT NULL')
# New hotness
User.where.not(name: nil)

not in系

# Without `where.not`
# Something.where("name NOT IN ?", User.unverified.pluck(:name))
# With `where.not`
Something.where.not(name: User.unverified.pluck(:name))