Created
July 17, 2012 19:55
Revisions
-
jessieay revised this gist
Jul 17, 2012 . 1 changed file with 50 additions and 52 deletions.There are no files selected for viewing
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode charactersOriginal file line number Diff line number Diff line change @@ -1,20 +1,22 @@ ActiveRecord cheat sheet / EXAMPLES INSTALL ======= $ gem install activerecord in GEMFILE: gem ‘activerecord’ REQUIRE ======= require ‘active_record’ HOW TO USE ESTABLISH A DATABASE CONNECTION ======= ActiveRecord::Base.establish_connection( :adapter => 'sqlite3', :database => 'database_path') CREATE TABLE IN DATABASE ======= ActiveRecord::Base.connection.execute <<-SQL CREATE TABLE IF NOT EXISTS students ( id INTEGER PRIMARY KEY AUTOINCREMENT, @@ -23,10 +25,8 @@ ActiveRecord::Base.connection.execute <<-SQL ); SQL RELATIONSHIPS ======= one-to-one: class Customer < ActiveRecord::Base @@ -37,24 +37,24 @@ class Detail < ActiveRecord::Base belongs_to :customer end ## to include automatic building of detail when instantiate a customer, add this to customer class: has_one :detail after_initialize do self.build_detail end ## to automatically destroy detail record when destroy customer record: has_one :detail, :dependent => :destroy ## to hide child object, add the following to parent class: delegate :birthday, :gender, :city, :to => :detail OR delegate *Detail::ATTR_METHODS, :to => :detail ## (must include ATTR_METHODS = [:birthday, :birthday=, :gender, :gender=, :city, :city=] in detail class to use 2nd option] one-to-many @@ -66,10 +66,10 @@ class Child < ActiveRecord::Base belongs_to :parent end ## to destroy chid objects when parent in destroyed, add the following to the parent class: has_many :children, :dependent => :destroy many-to-many @@ -82,46 +82,50 @@ class Customer < ActiveRecord::Base has_many :subscriptions has_many :magazines, :through => :subscriptions end ## this makes it easy to find a customer’s magazines: @customer = customer.find(17) @customer.magazines ## it also makes it easy to find a customer’s subscriptions: @customer.subscriptions CREATING RECORDS: ===================== Single/Parent: myStudent1 = Student.new(:first_name => 'Ann', :last_name => 'Smith', :birthday => '1986-08-11') myStudent1.save Child: (myStudent1.classes.new(:name => ‘Geometry’)).save ##note alternative method for saving and pluralized ‘classes’## QUERIES ===================== Find one by id: Customer.find(17) ## finds customer with an id of 17 Find related records by id: Customer.find(17).detail.birthday ## finds birthday field for the customer with id = 17. Birthday field is contained in Details table. Find by label: Can do: - Person.where(:user_name => user_name).first @@ -133,49 +137,53 @@ Better: - Person.find_all_by_last_name(last_name) - Person.find_by_user_name_and_password(user_name, password) List all: Contact.all.each do |contact| puts contact.first_name end ## puts of first name for each contact in Contacts table Conditional: Student.where(:gender => 'male') ## finds students with the value ‘male’ in the gender column LIKE: Contact.where("first_name LIKE 'A%'") OR Contact.where(‘first_name LIKE ?', “A%") ## both examples above find contacts where first_name column begins with A. Some people prefer second for stylistic reasons ## Using LIKE to find values in the middle of a string: Student.where("birthday LIKE '%-07-%'").each do |student| puts student.first_name + " has a birthday in July" end ## prints the first name of all students with birthdays in July Count: Client.count ## prints count of number of records in Client table Client.where(:first_name => 'Ryan').count ## prints the the count of clients where first_name is Ryan Unique: Client.select(:name).uniq ## only grabs a single record per unique value in the :name field ## A more complicated example using .uniq: contacts = Address.where(:state => 'CA').includes(:contact).collect do |address| address.contact @@ -185,18 +193,8 @@ contacts.uniq.each do |contact| puts contact end ## finds each address in CA and then prints out each contact with an address in CA only once ## Another way doing this (via http://whatcodecraves.com/articles/2009/04/08/adventures-with-active-record-find): Fruit.all(:select => "DISTINCT fruits.*", ...) -
Jul 17, 2012 . 1 changed file with 0 additions and 0 deletions.There are no files selected for viewing
File renamed without changes. -
Jul 17, 2012 . 1 changed file with 1 addition and 1 deletion.There are no files selected for viewing
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode charactersOriginal file line number Diff line number Diff line change @@ -25,6 +25,7 @@ SQL RELATIONSHIPS ======= one-to-one: @@ -199,4 +200,3 @@ Fruit.all(:select => "DISTINCT fruits.*", ...) -
Jul 17, 2012 .There are no files selected for viewing
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode charactersOriginal file line number Diff line number Diff line change @@ -0,0 +1,202 @@ ActiveRecord cheat sheet INSTALL ======= $ gem install activerecord HOW TO USE ESTABLISH A DATABASE CONNECTION ======= ActiveRecord::Base.establish_connection( :adapter => 'sqlite3', :database => 'database_path') CREATE TABLE IN DATABASE ======= ActiveRecord::Base.connection.execute <<-SQL CREATE TABLE IF NOT EXISTS students ( id INTEGER PRIMARY KEY AUTOINCREMENT, first_name VARCHAR NOT NULL, last_name VARCHAR NOT NULL, ); SQL RELATIONSHIPS one-to-one: class Customer < ActiveRecord::Base has_one :detail end class Detail < ActiveRecord::Base belongs_to :customer end ##to include automatic building of detail when instantiate a customer, add this to customer class:## has_one :detail after_initialize do self.build_detail end ## to automatically destroy detail record when destroy customer record:## has_one :detail, :dependent => :destroy ##to hide child object, add the following to parent class:## delegate :birthday, :gender, :city, :to => :detail OR delegate *Detail::ATTR_METHODS, :to => :detail ##(must include ATTR_METHODS = [:birthday, :birthday=, :gender, :gender=, :city, :city=] in detail class to use 2nd option]## one-to-many class Parent < ActiveRecord::Base has_many :children end class Child < ActiveRecord::Base belongs_to :parent end ##to destroy chid objects when parent in destroyed, add the following to the parent class:## has_many :children, :dependent => :destroy many-to-many class Magazine < ActiveRecord::Base has_many :subscriptions has_many :customers, :through => :subscriptions end class Customer < ActiveRecord::Base has_many :subscriptions has_many :magazines, :through => :subscriptions end ##to find a customer’s magazines:## @customer = customer.find(17) @customer.magazines ##to find a customer’s subscriptions:## @customer.subscriptions CREATING RECORDS: ===================== Single: myStudent1 = Student.new(:first_name => 'Ann', :last_name => 'Smith', :birthday => '1986-08-11') myStudent1.save Child: (myStudent1.classes.new(:name => ‘Geometry’)).save ##note alternative method for saving and pluralized ‘classes’## QUERIES ===================== Find one by id: Customer.find(17) ##finds customer with an id of 17## Find related records by id: Customer.find(17).detail.birthday ##finds birthday field for the customer with id = 17. Birthday field is contained in Details table.## Dynamic, attribute-based finders: Can do: - Person.where(:user_name => user_name).first - Person.where(:last_name => last_name).all - Person.where(:user_name => user_name, :password => password).first Better: - Person.find_by_user_name(user_name) - Person.find_all_by_last_name(last_name) - Person.find_by_user_name_and_password(user_name, password) List all: Contact.all.each do |contact| puts contact.first_name end ##puts of first name for each contact in Contacts table## Conditional: Student.where(:gender => 'male') ##finds students with the value ‘male’ in the gender column## LIKE: Contact.where("first_name LIKE 'A%'") OR Contact.where(‘first_name LIKE ?', “A%") ##both examples above find contacts where first_name column begins with A. Some people prefer second for stylistic reasons## Using LIKE to find values in the middle of a string: Student.where("birthday LIKE '%-07-%'").each do |student| puts student.first_name + " has a birthday in July" end ##prints the first name of all students with birthdays in July## Selecting unique values: Client.select(:name).uniq ##only grabs a single record per unique value in the :name field## A more complicated example using .uniq: contacts = Address.where(:state => 'CA').includes(:contact).collect do |address| address.contact end contacts.uniq.each do |contact| puts contact end ##finds each address in CA and then prints out each contact with an address in CA only once## Another way doing this (via http://whatcodecraves.com/articles/2009/04/08/adventures-with-active-record-find): Fruit.all(:select => "DISTINCT fruits.*", ...)