sheesh19 / 452-ar-advanced

ActiveRecord Boilerplate

This is a starting point for the Activerecord Basics lecture using sqlite. During the lecture, you need to:

• Clone The project
• Run bundle install
• Explain rake -T
• Explain config/database.yml
• Run rake db:create / rake db:drop
• Create and run 2 migrations

RELATIONSHIPS

• One to Many Relationship

• Many to Many Relationship (needs join table which has two foreign keys)

• One to One Relationship

• HAS MANY && BELONGS TO are keywords when you discuss databases

SQL QUERIES

• CREATE: INSERT INTO

• READ: SELECT

• UPDATE: UPDATE

• DELETE: DELETE FROM

• RETURN 10 PATIENTS FROM DOCTORS DATABASE

• SELECT * FROM patients LIMIT 10;

• RETURN EVERYTHING FROM DOCTORS & INTERNS TABLES

• SELECT *

• FROM doctors

• JOIN interns ON doctors.id = interns.doctor_id

• SQL: the language to query our database

ACTIVERECORD

• ActiveRecord: ruby library for the 'ruby magic', which lets us interact with our DB without SQL and creates instances for us. Links our Model & our database together.

• MIGRATION TO CREATE DOCTOR TABLE

• class CreateDoctors < ActiveRecord::Migration[5.1]

• def change create_table :doctors do |t| t.string :first_name t.string :last_name t.timestamps end

• end

• end

• class AddSpecialtyToDoctors < ActiveRecord::Migration[5.1]

• def change add_column :doctors, :specialty, :string

• end

• end

ACTIVERECORD QUERIES

• CREATE: Doctor.create(first_name: 'Gregory', last_name: 'House') <- Doctor.new + Doctor.save

• READ ALL: Doctor.all

• READ ONE: Doctor.find(1) <- put in ID

• READ ONE: Doctor.find_by(first_name: 'Gregory') <- returns first doctor with first_name Gregory

• READ ALL + QUERY: Doctor.where(first_name: 'Gregory') <- returns every doctor with first_name Gregory

• UPDATE: doctor = Doctor.find(1), doctor.first_name = 'New Name', doctor.save

• DELETE: doctor = Doctor.find(1), doctor.destroy

• RETURN last_name: doctor = Doctor.find(1), doctor.last_name

• RETURN LAST DOCTOR: Doctor.last

• RETURN FIRST DOCTOR: Doctor.first

• RETURN COUNT of DOCTORS: Doctor.count

• RETURN FIRST 5 DOCTORS: Doctor.first(5)