3 category: Ruby libraries
11 DB = Sequel.sqlite('my_blog.db')
12 DB = Sequel.connect('postgres://user:password@localhost/my_db')
13 DB = Sequel.postgres('my_db', :user => 'user', :password => 'password', :host => 'localhost')
14 DB = Sequel.ado('mydb')
16 ### Open an SQLite memory database
18 Without a filename argument, the sqlite adapter will setup a new sqlite database in memory.
22 ### Logging SQL statements
25 DB = Sequel.sqlite '', :loggers => [Logger.new($stdout)]
27 DB.loggers << Logger.new(...)
31 DB.run "CREATE TABLE users (name VARCHAR(255) NOT NULL, age INT(3) NOT NULL)"
32 dataset = DB["SELECT age FROM users WHERE name = ?", name]
34 DB.fetch("SELECT name FROM users") do |row|
41 dataset = DB.from(:items)
43 ### Most dataset methods are chainable
45 dataset = DB[:managers].where(:salary => 5000..10000).order(:name, :department)
49 dataset.insert(:name => 'Sharon', :grade => 50)
54 dataset.all # => [{...}, {...}, ...]
55 dataset.first # => {...}
57 ### Update/Delete rows
59 dataset.filter(~:active).delete
60 dataset.filter('price < ?', 100).update(:active => true)
62 ### Datasets are Enumerable
64 dataset.map{|r| r[:name]}
65 dataset.map(:name) # same as above
67 dataset.inject(0){|sum, r| sum + r[:value]}
68 dataset.sum(:value) # same as above
70 ### Filtering (see also doc/dataset_filtering.rdoc)
74 dataset.filter(:name => 'abc')
75 dataset.filter('name = ?', 'abc')
79 dataset.filter{value > 100}
80 dataset.exclude{value <= 100}
84 dataset.filter(:value => 50..100)
85 dataset.where{(value >= 50) & (value <= 100)}
87 dataset.where('value IN ?', [50,75,100])
88 dataset.where(:value=>[50,75,100])
90 dataset.where(:id=>other_dataset.select(:other_id))
92 #### Subselects as scalar values
94 dataset.where('price > (SELECT avg(price) + 100 FROM table)')
95 dataset.filter{price > dataset.select(avg(price) + 100)}
99 DB[:items].filter(:name.like('AL%'))
100 DB[:items].filter(:name => /^AL/)
104 DB[:items].filter{(x > 5) & (y > 10)}.sql
105 # SELECT * FROM items WHERE ((x > 5) AND (y > 10))
107 DB[:items].filter({:x => 1, :y => 2}.sql_or & ~{:z => 3}).sql
108 # SELECT * FROM items WHERE (((x = 1) OR (y = 2)) AND (z != 3))
110 #### Mathematical operators
112 DB[:items].filter((:x + :y) > :z).sql
113 # SELECT * FROM items WHERE ((x + y) > z)
115 DB[:items].filter{price - 100 < avg(price)}.sql
116 # SELECT * FROM items WHERE ((price - 100) < avg(price))
121 dataset.reverse_order(:kind)
122 dataset.order(:kind.desc, :name)
126 dataset.limit(30) # LIMIT 30
127 dataset.limit(30, 10) # LIMIT 30 OFFSET 10
131 DB[:items].left_outer_join(:categories, :id => :category_id).sql
132 # SELECT * FROM items LEFT OUTER JOIN categories ON categories.id = items.category_id
134 DB[:items].join(:categories, :id => :category_id).join(:groups, :id => :items__group_id)
135 # SELECT * FROM items INNER JOIN categories ON categories.id = items.category_id INNER JOIN groups ON groups.id = items.group_id
137 ### Aggregate functions methods
139 dataset.count #=> record count
145 dataset.group_and_count(:category)
146 dataset.group(:category).select(:category, :AVG.sql_function(:price))
148 ### SQL Functions / Literals
150 dataset.update(:updated_at => :NOW.sql_function)
151 dataset.update(:updated_at => 'NOW()'.lit)
153 dataset.update(:updated_at => "DateValue('1/1/2001')".lit)
154 dataset.update(:updated_at => :DateValue.sql_function('1/1/2001'))
156 ### Schema Manipulation
158 DB.create_table :items do
160 String :name, :unique => true, :null => false
161 TrueClass :active, :default => true
162 foreign_key :category_id, :categories
170 DB.create_table :test do
172 enum :system, :elements => ['mac', 'linux', 'windows']
177 DB[:items].select(:name.as(:item_name))
178 DB[:items].select(:name___item_name)
179 DB[:items___items_table].select(:items_table__name___item_name)
180 # SELECT items_table.name AS item_name FROM items AS items_table
185 dataset.insert(:first_name => 'Inigo', :last_name => 'Montoya')
186 dataset.insert(:first_name => 'Farm', :last_name => 'Boy')
187 end # Either both are inserted or neither are inserted
189 Database#transaction is re-entrant:
191 DB.transaction do # BEGIN issued only here
193 dataset << {:first_name => 'Inigo', :last_name => 'Montoya'}
195 end # COMMIT issued only here
197 Transactions are aborted if an error is raised:
200 raise "some error occurred"
201 end # ROLLBACK issued and the error is re-raised
203 Transactions can also be aborted by raising Sequel::Rollback:
206 raise(Sequel::Rollback) if something_bad_happened
207 end # ROLLBACK issued and no error raised
209 Savepoints can be used if the database supports it:
212 dataset << {:first_name => 'Farm', :last_name => 'Boy'} # Inserted
213 DB.transaction(:savepoint=>true) # This savepoint is rolled back
214 dataset << {:first_name => 'Inigo', :last_name => 'Montoya'} # Not inserted
215 raise(Sequel::Rollback) if something_bad_happened
217 dataset << {:first_name => 'Prince', :last_name => 'Humperdink'} # Inserted
222 dataset.sql # "SELECT * FROM items"
223 dataset.delete_sql # "DELETE FROM items"
224 dataset.where(:name => 'sequel').exists # "EXISTS ( SELECT * FROM items WHERE name = 'sequel' )"
225 dataset.columns #=> array of columns in the result set, does a SELECT
226 DB.schema(:items) => [[:id, {:type=>:integer, ...}], [:name, {:type=>:string, ...}], ...]
228 ----------------------------------------------------------------------------------------------------------------------------------------------------------------
232 http://sequel.rubyforge.org/rdoc/files/doc/association_basics_rdoc.html
233 http://sequel.rubyforge.org/rdoc/classes/Sequel/Schema/Generator.html
234 http://sequel.rubyforge.org/rdoc/files/doc/validations_rdoc.html
235 http://sequel.rubyforge.org/rdoc/classes/Sequel/Model.html
239 database.alter_table :deals do
240 add_column :name, String
241 drop_column :column_name
242 rename_column :from, :to
244 add_constraint :valid_name, :name.like('A%')
245 drop_constraint :constraint
247 add_full_text_index :body
248 add_spacial_index [columns]
253 add_foreign_key :artist_id, :table
255 add_unique_constraint [columns]
256 set_column_allow_null :foo, false
257 set_column_default :title, ''
259 set_column_type :price, 'char(10)'
262 ### Model associations
264 class Deal < Sequel::Model
266 # Us (left) <=> Them (right)
267 many_to_many :images,
270 join_table: :image_links
276 many_to_one :parent, class: self
277 one_to_many :children, key: :parent_id, class: self
279 one_to_many :gold_albums, class: :Album do |ds|
280 ds.filter { copies_sold > 50000 }
283 Provided by many_to_many
288 Deal[1].remove_all_images
294 errors.add(:name, 'cannot be empty') if !name || name.empty?
296 validates_presence [:title, :site]
297 validates_unique :name
298 validates_format /\Ahttps?:\/\//, :website, :message=>'is not a valid URL'
299 validates_includes %w(a b c), :type
300 validates_integer :rating
301 validates_numeric :number
302 validates_type String, [:title, :description]
304 validates_integer :rating if new?
306 # options: :message =>, :allow_nil =>, :allow_blank =>,
309 validates_exact_length 17, :isbn
310 validates_min_length 3, :name
311 validates_max_length 100, :name
312 validates_length_range 3..100, :name
316 @values[:filename] = name
327 deal.destroy # Calls hooks
328 deal.delete # No hooks
331 deal.hash # Only uniques
332 deal.keys #=> [:id, :name]
357 class Deal < Sequel::Model
360 primary_key [:id, :title]
361 String :name, primary_key: true
368 check(:price) { num > 0 }
370 foreign_key :artist_id
371 String :artist_name, key: :id
374 index [:artist_id, :name]
375 full_text_index :title
377 # String, Integer, Fixnum, Bignum, Float, Numeric, BigDecimal,
378 # Date, DateTime, Time, File, TrueClass, FalseClass
382 ### Unrestrict primary key
384 Category.create id: 'travel' # error
385 Category.unrestrict_primary_key
386 Category.create id: 'travel' # ok