ruby on rails sqlite的增删查改

sqlite 增删查改:

rails new premier_league
rails g model Team name point:integer
rails db:migrate

Team.create(name:"Man City", point: 20)
Team.create(name:"Liverpool", point: 20)
Team.create(name:"Chelsea", point: 20)
Team.create(name:"Tlsottenham", point: 18)
Team.create(name:"Arsenal", point: 18)
Team.create(name:"AFC Bournemouth", point: 16)
Team.create(name:"Wolverhampton", point: 15)
Team.create(name:"Watford", point: 13)
Team.create(name:"Manchester United", point: 13)
Team.create(name:"Leicester City", point: 12)
Team.create(name:"Everton", point: 12)
Team.create(name:"Burnley", point: 8)
Team.create(name:"Brighton", point: 8)
Team.create(name:"Crystal", point: 7)
Team.create(name:"West Ham", point: 7)
Team.create(name:"Southampton", point: 5)
Team.create(name:"Fulham", point: 5)
Team.create(name:"Huddersfield", point: 3)
Team.create(name:"Newcastle", point: 2)
Team.create(name:"Cardiff", point: 2)

rails db:reset






查
Team.find(1)
Team.find([1,3,5])

Team.where(point: 20)
Team.where(point: 12..16)
Team.where(point: [2, 20])

Team.where.not(point: 20)

//Team.where(point: 20).or(Team.where(name: “Arsenal”)

排序查
Team.all.order(:point)

Team.all.order(:point).reverse_order

Team.all.order(:point).reverse_order.limit(4)

Team.all.limit(2).offset(4)

Team.count
查
Team.maximum(:point)

Team.minimum(:point)

Team.average(:point)

t=Team.average(:point)

t.class
平均值
Team.average(:point).to_s

s=Team.average(:point).to_s

s.class
查
Team.where(point:10..16).find_each do |item|
puts item.name
end

改
Team.order(;point).reverse_order.first

team = Team.order(;point).reverse_order.first
team.class
team
team.name="blue moon"
team.save

team.name = "Man City"
team.name_changed?