413 lines
11 KiB
HTML
413 lines
11 KiB
HTML
<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8" />
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<title></title>
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<link href="style.css" rel="stylesheet" />
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</head>
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<body>
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<h1>Sequel</h1>
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<h1>Cheat Sheet </h1>
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<h2>Open a database</h2>
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<pre>
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require 'rubygems'
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require 'sequel'
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DB = Sequel.sqlite('my_blog.db')
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DB = Sequel.connect('postgres://user:password@localhost/my_db')
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DB = Sequel.postgres('my_db', :user => 'user', :password => 'password', :host => 'localhost')
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DB = Sequel.ado('mydb')
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</pre>
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<h2>Open an SQLite memory database</h2>
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<p>
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Without a filename argument, the sqlite adapter will setup a new sqlite
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database in memory.
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</p>
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<pre>
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DB = Sequel.sqlite
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</pre>
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<h2>Logging SQL statements</h2>
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<pre>
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require 'logger'
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DB = Sequel.sqlite '', :loggers => [Logger.new($stdout)]
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# or
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DB.loggers << Logger.new(...)
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</pre>
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<h2>Using raw SQL</h2>
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<pre>
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DB.run "CREATE TABLE users (name VARCHAR(255) NOT NULL, age INT(3) NOT NULL)"
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dataset = DB["SELECT age FROM users WHERE name = ?", name]
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dataset.map(:age)
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DB.fetch("SELECT name FROM users") do |row|
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p row[:name]
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end
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</pre>
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<h2>Create a dataset</h2>
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<pre>
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dataset = DB[:items]
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dataset = DB.from(:items)
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</pre>
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<h2>Most dataset methods are chainable</h2>
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<pre>
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dataset = DB[:managers].where(:salary => 5000..10000).order(:name, :department)
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</pre>
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<h2>Insert rows</h2>
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<pre>
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dataset.insert(:name => 'Sharon', :grade => 50)
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</pre>
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<h2>Retrieve rows</h2>
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<pre>
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dataset.each{|r| p r}
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dataset.all # => [{...}, {...}, ...]
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dataset.first # => {...}
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</pre>
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<h2>Update/Delete rows</h2>
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<pre>
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dataset.filter(~:active).delete
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dataset.filter('price < ?', 100).update(:active => true)
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</pre>
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<h2>Datasets are Enumerable</h2>
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<pre>
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dataset.map{|r| r[:name]}
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dataset.map(:name) # same as above
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dataset.inject(0){|sum, r| sum + r[:value]}
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dataset.sum(:value) # same as above
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</pre>
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<h2>Filtering (see also doc/dataset_filtering.rdoc)</h2>
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<h3>Equality</h3>
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<pre>
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dataset.filter(:name => 'abc')
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dataset.filter('name = ?', 'abc')
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</pre>
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<h3>Inequality</h3>
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<pre>
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dataset.filter{value > 100}
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dataset.exclude{value <= 100}
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</pre>
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<h3>Inclusion</h3>
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<pre>
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dataset.filter(:value => 50..100)
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dataset.where{(value >= 50) & (value <= 100)}
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dataset.where('value IN ?', [50,75,100])
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dataset.where(:value=>[50,75,100])
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dataset.where(:id=>other_dataset.select(:other_id))
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</pre>
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<h3>Subselects as scalar values</h3>
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<pre>
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dataset.where('price > (SELECT avg(price) + 100 FROM table)')
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dataset.filter{price > dataset.select(avg(price) + 100)}
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</pre>
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<h3>LIKE/Regexp</h3>
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<pre>
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DB[:items].filter(:name.like('AL%'))
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DB[:items].filter(:name => /^AL/)
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</pre>
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<h3>AND/OR/NOT</h3>
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<pre>
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DB[:items].filter{(x > 5) & (y > 10)}.sql
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# SELECT * FROM items WHERE ((x > 5) AND (y > 10))
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DB[:items].filter({:x => 1, :y => 2}.sql_or & ~{:z => 3}).sql
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# SELECT * FROM items WHERE (((x = 1) OR (y = 2)) AND (z != 3))
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</pre>
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<h3>Mathematical operators</h3>
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<pre>
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DB[:items].filter((:x + :y) > :z).sql
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# SELECT * FROM items WHERE ((x + y) > z)
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DB[:items].filter{price - 100 < avg(price)}.sql
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# SELECT * FROM items WHERE ((price - 100) < avg(price))
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</pre>
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<h2>Ordering</h2>
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<pre>
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dataset.order(:kind)
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dataset.reverse_order(:kind)
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dataset.order(:kind.desc, :name)
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</pre>
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<h2>Limit/Offset</h2>
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<pre>
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dataset.limit(30) # LIMIT 30
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dataset.limit(30, 10) # LIMIT 30 OFFSET 10
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</pre>
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<h2>Joins</h2>
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<pre>
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DB[:items].left_outer_join(:categories, :id => :category_id).sql
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# SELECT * FROM items LEFT OUTER JOIN categories ON categories.id = items.category_id
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DB[:items].join(:categories, :id => :category_id).join(:groups, :id => :items__group_id)
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# SELECT * FROM items INNER JOIN categories ON categories.id = items.category_id INNER JOIN groups ON groups.id = items.group_id
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</pre>
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<p>
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</p>
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<h2>Aggregate functions methods</h2>
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<pre>
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dataset.count #=> record count
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dataset.max(:price)
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dataset.min(:price)
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dataset.avg(:price)
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dataset.sum(:stock)
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dataset.group_and_count(:category)
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dataset.group(:category).select(:category, :AVG.sql_function(:price))
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</pre>
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<h2>SQL Functions / Literals</h2>
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<pre>
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dataset.update(:updated_at => :NOW.sql_function)
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dataset.update(:updated_at => 'NOW()'.lit)
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dataset.update(:updated_at => "DateValue('1/1/2001')".lit)
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dataset.update(:updated_at => :DateValue.sql_function('1/1/2001'))
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</pre>
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<h2>Schema Manipulation</h2>
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<pre>
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DB.create_table :items do
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primary_key :id
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String :name, :unique => true, :null => false
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TrueClass :active, :default => true
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foreign_key :category_id, :categories
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DateTime :created_at
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index :created_at
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end
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DB.drop_table :items
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DB.create_table :test do
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String :zipcode
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enum :system, :elements => ['mac', 'linux', 'windows']
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end
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</pre>
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<h2>Aliasing</h2>
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<pre>
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DB[:items].select(:name.as(:item_name))
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DB[:items].select(:name___item_name)
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DB[:items___items_table].select(:items_table__name___item_name)
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# SELECT items_table.name AS item_name FROM items AS items_table
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</pre>
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<h2>Transactions</h2>
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<pre>
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DB.transaction do
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dataset.insert(:first_name => 'Inigo', :last_name => 'Montoya')
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dataset.insert(:first_name => 'Farm', :last_name => 'Boy')
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end # Either both are inserted or neither are inserted
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</pre>
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<p>
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Database#transaction is re-entrant:
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</p>
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<pre>
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DB.transaction do # BEGIN issued only here
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DB.transaction
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dataset << {:first_name => 'Inigo', :last_name => 'Montoya'}
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end
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end # COMMIT issued only here
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</pre>
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<p>
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Transactions are aborted if an error is raised:
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</p>
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<pre>
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DB.transaction do
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raise "some error occurred"
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end # ROLLBACK issued and the error is re-raised
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</pre>
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<p>
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Transactions can also be aborted by raising Sequel::Rollback:
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</p>
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<pre>
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DB.transaction do
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raise(Sequel::Rollback) if something_bad_happened
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end # ROLLBACK issued and no error raised
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</pre>
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<p>
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Savepoints can be used if the database supports it:
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</p>
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<pre>
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DB.transaction do
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dataset << {:first_name => 'Farm', :last_name => 'Boy'} # Inserted
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DB.transaction(:savepoint=>true) # This savepoint is rolled back
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dataset << {:first_name => 'Inigo', :last_name => 'Montoya'} # Not inserted
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raise(Sequel::Rollback) if something_bad_happened
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end
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dataset << {:first_name => 'Prince', :last_name => 'Humperdink'} # Inserted
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end
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</pre>
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<h2>Miscellaneous:</h2>
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<pre>
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dataset.sql # "SELECT * FROM items"
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dataset.delete_sql # "DELETE FROM items"
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dataset.where(:name => 'sequel').exists # "EXISTS ( SELECT * FROM items WHERE name = 'sequel' )"
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dataset.columns #=> array of columns in the result set, does a SELECT
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DB.schema(:items) => [[:id, {:type=>:integer, ...}], [:name, {:type=>:string, ...}], ...]
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</pre>
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<hr style="height: 10px"></hr><h2>Documents</h2>
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<pre>
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http://sequel.rubyforge.org/rdoc/files/doc/association_basics_rdoc.html
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http://sequel.rubyforge.org/rdoc/classes/Sequel/Schema/Generator.html
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http://sequel.rubyforge.org/rdoc/files/doc/validations_rdoc.html
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http://sequel.rubyforge.org/rdoc/classes/Sequel/Model.html
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</pre>
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<h2>Alter table</h2>
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<pre>
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database.alter_table :deals do
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add_column :name, String
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drop_column :column_name
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rename_column :from, :to
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add_constraint :valid_name, :name.like('A%')
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drop_constraint :constraint
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add_full_text_index :body
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add_spacial_index [columns]
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add_index :price
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drop_index :index
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add_foreign_key :artist_id, :table
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add_primary_key :id
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add_unique_constraint [columns]
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set_column_allow_null :foo, false
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set_column_default :title, ''
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set_column_type :price, 'char(10)'
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end
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</pre>
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<h2>Model associations</h2>
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<pre>
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class Deal < Sequel::Model
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# Us (left) <=> Them (right)
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many_to_many :images,
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left_id: :deal_id,
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right_id: :image_id,
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join_table: :image_links
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one_to_many :files,
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key: :deal_id,
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class: :DataFile,
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many_to_one :parent, class: self
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one_to_many :children, key: :parent_id, class: self
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one_to_many :gold_albums, class: :Album do |ds|
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ds.filter { copies_sold > 50000 }
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end
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</pre>
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<p>
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Provided by many_to_many
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</p>
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<pre>
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Deal[1].images
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Deal[1].add_image
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Deal[1].remove_image
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Deal[1].remove_all_images
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</pre>
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<h2>Validations</h2>
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<pre>
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def validate
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super
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errors.add(:name, 'cannot be empty') if !name || name.empty?
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validates_presence [:title, :site]
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validates_unique :name
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validates_format /\Ahttps?:\/\//, :website, :message=>'is not a valid URL'
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validates_includes %w(a b c), :type
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validates_integer :rating
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validates_numeric :number
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validates_type String, [:title, :description]
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validates_integer :rating if new?
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# options: :message =>, :allow_nil =>, :allow_blank =>,
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# :allow_missing =>,
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validates_exact_length 17, :isbn
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validates_min_length 3, :name
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validates_max_length 100, :name
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validates_length_range 3..100, :name
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# Setter override
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def filename=(name)
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@values[:filename] = name
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end
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end
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end
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deal.errors
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</pre>
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<h2>Model stuff</h2>
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<pre>
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deal = Deal[1]
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deal.changed_columns
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deal.destory # Calls hooks
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deal.delete # No hooks
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deal.exists?
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deal.new?
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deal.hash # Only uniques
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deal.keys #=> [:id, :name]
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deal.modified!
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deal.modified?
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deal.lock!
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</pre>
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<h2>Callbacks</h2>
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<pre>
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before_create
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after_create
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before_validation
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after_validation
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before_save
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before_update
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UPDATE QUERY
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after_update
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after_save
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before_destroy
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DELETE QUERY
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after_destroy
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</pre>
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<h2>Schema</h2>
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<pre>
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class Deal < Sequel::Model
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set_schema do
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primary_key :id
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primary_key [:id, :title]
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String :name, primary_key: true
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String :title
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Numeric :price
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DateTime :expires
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unique :whatever
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check(:price) { num > 0 }
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foreign_key :artist_id
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String :artist_name, key: :id
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index :title
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index [:artist_id, :name]
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full_text_index :title
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# String, Integer, Fixnum, Bignum, Float, Numeric, BigDecimal,
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# Date, DateTime, Time, File, TrueClass, FalseClass
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end
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end
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</pre>
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<h2>Unrestrict primary key</h2>
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<pre>
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Category.create id: 'travel' # error
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Category.unrestrict_primary_key
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Category.create id: 'travel' # ok
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</pre>
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<script src='http://cdnjs.cloudflare.com/ajax/libs/jquery/1.6.4/jquery.min.js'></script>
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<script src="http://cachedcommons.org/cache/prettify/1.0.0/javascripts/prettify-min.js"></script>
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<script>$("pre").addClass("prettyprint");</script>
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<script>prettyPrint();</script>
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</body>
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</html>
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