337 lines
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This is <a href="."><em>Devhints.io cheatsheets</em></a> — a collection of cheatsheets I've written.
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<div class='post-headline -cheatsheet'>
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<p class='prelude'><span></span></p>
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<h1><span>Migrations</span></h1>
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<div class='post-content -cheatsheet'>
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<h3 id="automatically-make-migrations">Automatically make migrations</h3>
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<pre><code>$ rails generate migration RemovePartNumberFromProducts part_number:string
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$ rails generate migration remove_part_number_from_products part_number # rails assumes string if not type given - and you can use snake_case
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$ rails generate migration AddNameToWidgets name:string
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$ rails g migration add_name_to_widgets name:string # you can use the short cut 'g' instead of generate - they both do the same thing
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</code></pre>
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<h3 id="run-migrations">Run migrations</h3>
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<pre><code>$ rake db:migrate
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</code></pre>
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<h3 id="creating-tables">Creating tables</h3>
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<pre><code>create_table :users do |t|
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t.string :name
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t.text :description
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t.primary_key :id
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t.string :title
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t.text :description
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t.integer :games_count
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t.float :lol
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t.decimal :price
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t.decimal :price, :precision => 2, :scale => 10
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t.datetime :expiration
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t.timestamp :time_in
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t.time :time_in
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t.date :expiry
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t.binary :image_data
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t.boolean :is_admin
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end
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# Options:
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:null (boolean)
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:limit (integer)
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:default
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</code></pre>
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<h3 id="operations">Operations</h3>
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<pre><code>add_column :users, :first_name, :string
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remove_column :users, :first_name, :string
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change_column :users, :first_name, :text
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change_column_default :users, :admin, nil
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change_column_null :users, :email, false # adds NOT NULL constraint
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create_table
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change_table
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drop_table
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add_column
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change_column
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rename_column
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remove_column
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add_index
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remove_index
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</code></pre>
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<h3 id="use-models">Use models</h3>
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<pre><code>class AddFlagToProduct < ActiveRecord::Migration
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class Product < ActiveRecord::Base
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end
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def change
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add_column :products, :flag, :boolean
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Product.reset_column_information
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reversible do |dir|
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dir.up { Product.update_all flag: false }
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end
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end
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end
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</code></pre>
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<h3 id="associations">Associations</h3>
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<pre><code>t.references :category # kinda same as t.integer :category_id
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# Can have different types
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t.references :category, polymorphic: true
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</code></pre>
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<h3 id="auto-addremove-columns">Auto-Add/remove columns</h3>
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<pre><code>$ rails generate migration RemovePartNumberFromProducts part_number:string
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</code></pre>
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<h3 id="indices">Indices</h3>
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<pre><code># Simple
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add_index :suppliers, :name
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# Unique
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add_index :accounts, [:branch_id, :party_id], :unique => true
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# Named (:name => ...)
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add_index :accounts, [:branch_id, :party_id], :unique => true, :name => "by_branch_party"
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# Length
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add_index :accounts, :name, :name => ‘by_name’, :length => 10
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add_index :accounts, [:name, :surname], :name => ‘by_name_surname’,
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:length => {
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:name => 10,
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:surname => 15
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}
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# Sort order (no MySQL support)
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add_index :accounts, [:branch_id, :party_id, :surname],
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:order => {:branch_id => :desc, :part_id => :asc}
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</code></pre>
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<h3 id="in-console">In console</h3>
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<p>Use <code>ActiveRecord::Migration</code>.</p>
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<pre><code>ActiveRecord::Migration.add_index :posts, :slug
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</code></pre>
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<h3 id="references">References</h3>
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<ul>
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<li>http://apidock.com/rails/ActiveRecord/ConnectionAdapters/SchemaStatements/add_index</li>
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<p class='blurb'>
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<strong><a href=".">Devhints.io cheatsheets</a></strong> is a collection of cheatsheets I've written over the years.
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Suggestions and corrections? <a href='https://github.com/rstacruz/cheatsheets/issues/907'>Send them in</a>.
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<i class='fleuron'></i>
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I'm <a href="http://ricostacruz.com">Rico Sta. Cruz</a>.
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Check out my <a href="http://ricostacruz.com/til">Today I learned blog</a> for more.
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