3 category: Ruby libraries
11 Sequel is a database toolkit for Ruby.
13 - <https://github.com/jeremyevans/sequel>
21 DB = Sequel.sqlite('my_blog.db')
22 DB = Sequel.connect('postgres://user:password@localhost/my_db')
23 DB = Sequel.postgres('my_db', :user => 'user', :password => 'password', :host => 'localhost')
24 DB = Sequel.ado('mydb')
27 ### Open an SQLite memory database
29 Without a filename argument, the sqlite adapter will setup a new sqlite database in memory.
35 ### Logging SQL statements
39 DB = Sequel.sqlite '', :loggers => [Logger.new($stdout)]
41 DB.loggers << Logger.new(...)
47 DB.run "CREATE TABLE users (name VARCHAR(255) NOT NULL, age INT(3) NOT NULL)"
48 dataset = DB["SELECT age FROM users WHERE name = ?", name]
50 DB.fetch("SELECT name FROM users") do |row|
59 dataset = DB.from(:items)
62 ### Most dataset methods are chainable
65 dataset = DB[:managers].where(:salary => 5000..10000).order(:name, :department)
71 dataset.insert(:name => 'Sharon', :grade => 50)
78 dataset.all # => [{...}, {...}, ...]
79 dataset.first # => {...}
82 ### Update/Delete rows
85 dataset.filter(~:active).delete
86 dataset.filter('price < ?', 100).update(:active => true)
89 ### Datasets are Enumerable
92 dataset.map{|r| r[:name]}
93 dataset.map(:name) # same as above
95 dataset.inject(0){|sum, r| sum + r[:value]}
96 dataset.sum(:value) # same as above
99 ### Filtering (see also doc/dataset_filtering.rdoc)
104 dataset.filter(:name => 'abc')
105 dataset.filter('name = ?', 'abc')
111 dataset.filter{value > 100}
112 dataset.exclude{value <= 100}
118 dataset.filter(:value => 50..100)
119 dataset.where{(value >= 50) & (value <= 100)}
121 dataset.where('value IN ?', [50,75,100])
122 dataset.where(:value=>[50,75,100])
124 dataset.where(:id=>other_dataset.select(:other_id))
127 #### Subselects as scalar values
130 dataset.where('price > (SELECT avg(price) + 100 FROM table)')
131 dataset.filter{price > dataset.select(avg(price) + 100)}
137 DB[:items].filter(:name.like('AL%'))
138 DB[:items].filter(:name => /^AL/)
144 DB[:items].filter{(x > 5) & (y > 10)}.sql
145 # SELECT * FROM items WHERE ((x > 5) AND (y > 10))
147 DB[:items].filter({:x => 1, :y => 2}.sql_or & ~{:z => 3}).sql
148 # SELECT * FROM items WHERE (((x = 1) OR (y = 2)) AND (z != 3))
151 #### Mathematical operators
154 DB[:items].filter((:x + :y) > :z).sql
155 # SELECT * FROM items WHERE ((x + y) > z)
157 DB[:items].filter{price - 100 < avg(price)}.sql
158 # SELECT * FROM items WHERE ((price - 100) < avg(price))
165 dataset.reverse_order(:kind)
166 dataset.order(:kind.desc, :name)
172 dataset.limit(30) # LIMIT 30
173 dataset.limit(30, 10) # LIMIT 30 OFFSET 10
179 DB[:items].left_outer_join(:categories, :id => :category_id).sql
180 # SELECT * FROM items LEFT OUTER JOIN categories ON categories.id = items.category_id
182 DB[:items].join(:categories, :id => :category_id).join(:groups, :id => :items__group_id)
183 # SELECT * FROM items INNER JOIN categories ON categories.id = items.category_id INNER JOIN groups ON groups.id = items.group_id
186 ### Aggregate functions methods
189 dataset.count #=> record count
195 dataset.group_and_count(:category)
196 dataset.group(:category).select(:category, :AVG.sql_function(:price))
199 ### SQL Functions / Literals
202 dataset.update(:updated_at => :NOW.sql_function)
203 dataset.update(:updated_at => 'NOW()'.lit)
205 dataset.update(:updated_at => "DateValue('1/1/2001')".lit)
206 dataset.update(:updated_at => :DateValue.sql_function('1/1/2001'))
209 ### Schema Manipulation
212 DB.create_table :items do
214 String :name, :unique => true, :null => false
215 TrueClass :active, :default => true
216 foreign_key :category_id, :categories
224 DB.create_table :test do
226 enum :system, :elements => ['mac', 'linux', 'windows']
233 DB[:items].select(:name.as(:item_name))
234 DB[:items].select(:name___item_name)
235 DB[:items___items_table].select(:items_table__name___item_name)
236 # SELECT items_table.name AS item_name FROM items AS items_table
243 dataset.insert(:first_name => 'Inigo', :last_name => 'Montoya')
244 dataset.insert(:first_name => 'Farm', :last_name => 'Boy')
245 end # Either both are inserted or neither are inserted
248 Database#transaction is re-entrant:
251 DB.transaction do # BEGIN issued only here
253 dataset << {:first_name => 'Inigo', :last_name => 'Montoya'}
255 end # COMMIT issued only here
258 Transactions are aborted if an error is raised:
262 raise "some error occurred"
263 end # ROLLBACK issued and the error is re-raised
266 Transactions can also be aborted by raising Sequel::Rollback:
270 raise(Sequel::Rollback) if something_bad_happened
271 end # ROLLBACK issued and no error raised
274 Savepoints can be used if the database supports it:
278 dataset << {:first_name => 'Farm', :last_name => 'Boy'} # Inserted
279 DB.transaction(:savepoint=>true) # This savepoint is rolled back
280 dataset << {:first_name => 'Inigo', :last_name => 'Montoya'} # Not inserted
281 raise(Sequel::Rollback) if something_bad_happened
283 dataset << {:first_name => 'Prince', :last_name => 'Humperdink'} # Inserted
290 dataset.sql # "SELECT * FROM items"
291 dataset.delete_sql # "DELETE FROM items"
292 dataset.where(:name => 'sequel').exists # "EXISTS ( SELECT * FROM items WHERE name = 'sequel' )"
293 dataset.columns #=> array of columns in the result set, does a SELECT
294 DB.schema(:items) => [[:id, {:type=>:integer, ...}], [:name, {:type=>:string, ...}], ...]
302 http://sequel.rubyforge.org/rdoc/files/doc/association_basics_rdoc.html
303 http://sequel.rubyforge.org/rdoc/classes/Sequel/Schema/Generator.html
304 http://sequel.rubyforge.org/rdoc/files/doc/validations_rdoc.html
305 http://sequel.rubyforge.org/rdoc/classes/Sequel/Model.html
311 database.alter_table :deals do
312 add_column :name, String
313 drop_column :column_name
314 rename_column :from, :to
316 add_constraint :valid_name, :name.like('A%')
317 drop_constraint :constraint
319 add_full_text_index :body
320 add_spacial_index [columns]
325 add_foreign_key :artist_id, :table
327 add_unique_constraint [columns]
328 set_column_allow_null :foo, false
329 set_column_default :title, ''
331 set_column_type :price, 'char(10)'
335 ### Model associations
338 class Deal < Sequel::Model
340 # Us (left) <=> Them (right)
341 many_to_many :images,
343 right_key: :image_id,
344 join_table: :image_links
350 many_to_one :parent, class: self
351 one_to_many :children, key: :parent_id, class: self
353 one_to_many :gold_albums, class: :Album do |ds|
354 ds.filter { copies_sold > 50000 }
358 Provided by many_to_many
364 Deal[1].remove_all_images
372 errors.add(:name, 'cannot be empty') if !name || name.empty?
374 validates_presence [:title, :site]
375 validates_unique :name
376 validates_format /\Ahttps?:\/\//, :website, :message=>'is not a valid URL'
377 validates_includes %w(a b c), :type
378 validates_integer :rating
379 validates_numeric :number
380 validates_type String, [:title, :description]
382 validates_integer :rating if new?
384 # options: :message =>, :allow_nil =>, :allow_blank =>,
387 validates_exact_length 17, :isbn
388 validates_min_length 3, :name
389 validates_max_length 100, :name
390 validates_length_range 3..100, :name
394 @values[:filename] = name
407 deal.destroy # Calls hooks
408 deal.delete # No hooks
411 deal.hash # Only uniques
412 deal.keys #=> [:id, :name]
441 class Deal < Sequel::Model
444 primary_key [:id, :title]
445 String :name, primary_key: true
452 check(:price) { num > 0 }
454 foreign_key :artist_id
455 String :artist_name, key: :id
458 index [:artist_id, :name]
459 full_text_index :title
461 # String, Integer, Fixnum, Bignum, Float, Numeric, BigDecimal,
462 # Date, DateTime, Time, File, TrueClass, FalseClass
467 ### Unrestrict primary key
470 Category.create id: 'travel' # error
471 Category.unrestrict_primary_key
472 Category.create id: 'travel' # ok