active records retrieve commands - week 3

20170413ActiveRecordsRetrieval

$ bundle install
$ bundle exec rake db:create
$ bundle exec rake db:migrate
$ bundle exec rake db:seed


bundle exec rake console

Dog.all

The SQL executed is equivalent to SELECT "dogs".* FROM "dogs" WHERE "dogs"."age" = 1.

Dog.where("age = ? and name like ?", 1, '%Te%')
equivalent of where in sql 

Dog.order(age: :desc)

descending, table name is dog
age is the attribute


Dog.limit(2)

returns active record objects


equivalent of count Dog.count

Dog.pluck(:name, :age)

selecting two attributes or columns 

pluck is just two fields 

Dog.first

just the first object in the table 

Dog.find(3) 

basically an id of 3 

Dog.find [1, 3] 

finding two ids 

Dog.find_by(name: "Jayda")

find is diff from where bc where outputs a collection of objects
whereas find_by only returns one - and the first one 

Dog.find_by(name: "Poop") outputs nil 

Dog.order(name: :asc).where(age: 1).limit(1) 

chaining methods