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90 changes: 45 additions & 45 deletions README.rdoc
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Expand Up @@ -26,40 +26,40 @@ toolkit for Ruby.
* {RDoc}[http://sequel.rubyforge.org/rdoc]

To check out the source code:

git clone git://github.com/jeremyevans/sequel.git

=== Contact

If you have any comments or suggestions please post to the Google group.

== Installation

sudo gem install sequel

== A Short Example

require 'rubygems'
require 'sequel'

DB = Sequel.sqlite # memory database

DB.create_table :items do
primary_key :id
String :name
Float :price
end

items = DB[:items] # Create a dataset

# Populate the table
items.insert(:name => 'abc', :price => rand * 100)
items.insert(:name => 'def', :price => rand * 100)
items.insert(:name => 'ghi', :price => rand * 100)

# Print out the number of records
puts "Item count: #{items.count}"

# Print out the average price
puts "The average price is: #{items.avg(:price)}"

Expand All @@ -82,7 +82,7 @@ Sequel uses the concept of datasets to retrieve data. A Dataset object encapsula
For example, the following one-liner returns the average GDP for countries in the middle east region:

DB[:countries].filter(:region => 'Middle East').avg(:GDP)

Which is equivalent to:

SELECT avg(GDP) FROM countries WHERE region = 'Middle East'
Expand All @@ -91,11 +91,11 @@ Since datasets retrieve records only when needed, they can be stored and later r

middle_east = DB[:countries].filter(:region => 'Middle East')
middle_east.order(:name).each{|r| puts r[:name]}

Sequel also offers convenience methods for extracting data from Datasets, such as an extended +map+ method:

middle_east.map(:name) #=> ['Egypt', 'Turkey', 'Israel', ...]

Or getting results as a hash via +to_hash+, with one column as key and another as value:

middle_east.to_hash(:name, :area) #=> {'Israel' => 20000, 'Turkey' => 120000, ...}
Expand All @@ -108,7 +108,7 @@ To connect to a database you simply provide <tt>Sequel.connect</tt> with a URL:

require 'sequel'
DB = Sequel.connect('sqlite://blog.db')

The connection URL can also include such stuff as the user name, password, and port:

DB = Sequel.connect('postgres://user:password@host:port/database_name')
Expand Down Expand Up @@ -174,49 +174,49 @@ Or perform more advanced stuff:

names_and_dates = posts.map([:name, :date])
old_posts, recent_posts = posts.partition{|r| r[:date] < Date.today - 7}

You can also retrieve the first record in a dataset:

posts.first
# SELECT * FROM posts LIMIT 1

Or retrieve a single record with a specific value:

posts[:id => 1]
# SELECT * FROM posts WHERE id = 1 LIMIT 1

If the dataset is ordered, you can also ask for the last record:

posts.order(:stamp).last
# SELECT * FROM posts ORDER BY stamp DESC LIMIT 1

=== Filtering Records

An easy way to filter records is to provide a hash of values to match to +where+:

my_posts = posts.where(:category => 'ruby', :author => 'david')
# WHERE category = 'ruby' AND author = 'david'

You can also specify ranges:

my_posts = posts.where(:stamp => (Date.today - 14)..(Date.today - 7))
# WHERE stamp >= '2010-06-30' AND stamp <= '2010-07-07'

Or arrays of values:

my_posts = posts.where(:category => ['ruby', 'postgres', 'linux'])
# WHERE category IN ('ruby', 'postgres', 'linux')

Sequel also accepts expressions:

my_posts = posts.where{stamp > Date.today << 1}
# WHERE stamp > '2010-06-14'

Some adapters will also let you specify Regexps:

my_posts = posts.where(:category => /ruby/i)
# WHERE category ~* 'ruby'

You can also use an inverse filter via +exclude+:

my_posts = posts.exclude(:category => ['ruby', 'postgres', 'linux'])
Expand All @@ -241,7 +241,7 @@ Datasets can also be used as subqueries:
After filtering, you can retrieve the matching records by using any of the retrieval methods:

my_posts.each{|row| p row}

See the {Dataset Filtering}[link:files/doc/dataset_filtering_rdoc.html] file for more details.

=== Summarizing Records
Expand All @@ -255,17 +255,17 @@ And you can also query maximum/minimum values via +max+ and +min+:

max = DB[:history].max(:value)
# SELECT max(value) FROM history

min = DB[:history].min(:value)
# SELECT min(value) FROM history

Or calculate a sum or average via +sum+ and +avg+:

sum = DB[:items].sum(:price)
# SELECT sum(price) FROM items
avg = DB[:items].avg(:price)
# SELECT avg(price) FROM items

=== Ordering Records

Ordering datasets is simple using +order+:
Expand All @@ -284,12 +284,12 @@ The +order_append+ method chains this way, though:

posts.order(:stamp).order_append(:name)
# ORDER BY stamp, name

The +order_prepend+ method can be used as well:

posts.order(:stamp).order_prepend(:name)
# ORDER BY name, stamp

You can also specify descending order:

posts.reverse_order(:stamp)
Expand Down Expand Up @@ -325,14 +325,14 @@ As you might expect, there is an +order_append+ equivalent for +select+ called +

posts.select(:stamp).select_append(:name)
# SELECT stamp, name FROM posts

=== Deleting Records

Deleting records from the table is done with +delete+:

posts.where('stamp < ?', Date.today - 3).delete
# DELETE FROM posts WHERE stamp < '2010-07-11'

Be very careful when deleting, as +delete+ affects all rows in the dataset.
Call +where+ first and +delete+ second:

Expand All @@ -347,7 +347,7 @@ Inserting records into the table is done with +insert+:

posts.insert(:category => 'ruby', :author => 'david')
# INSERT INTO posts (category, author) VALUES ('ruby', 'david')

=== Updating Records

Updating records in the table is done with +update+:
Expand Down Expand Up @@ -397,7 +397,7 @@ Sequel makes it easy to join tables:
order_items = DB[:items].join(:order_items, :item_id => :id).
where(:order_id => 1234)
# SELECT * FROM items INNER JOIN order_items
# ON order_items.item_id = items.id
# ON order_items.item_id = items.id
# WHERE order_id = 1234

The important thing to note here is that item_id is automatically qualified with
Expand All @@ -410,7 +410,7 @@ You can then do anything you like with the dataset:
# SELECT sum(price) FROM items INNER JOIN order_items
# ON order_items.item_id = items.id
# WHERE order_items.order_id = 1234

=== Graphing Datasets

When retrieving records from joined datasets, you get the results in a single hash, which is subject to clobbering if you have columns with the same name in multiple tables:
Expand Down Expand Up @@ -550,7 +550,7 @@ You can read the record values as object attributes, assuming the attribute name

post.id #=> 123
post.title #=> 'hello world'

If the record's attributes names are not valid columns in the model's dataset (maybe because you used +select_append+ to add a computed value column), you can use <tt>Model#[]</tt> to access the values:

post[:id] #=> 123
Expand All @@ -559,9 +559,9 @@ If the record's attributes names are not valid columns in the model's dataset (m
You can also modify record values using attribute setters, the <tt>[]=</tt> method, or the +set+ method:

post.title = 'hey there'
# or
# or
post[:title] = 'hey there'
# or
# or
post.set(:title=>'hey there')

That will just change the value for the object, it will not update the row in the database. To update the database row, call the +save+ method:
Expand Down Expand Up @@ -624,8 +624,8 @@ Records can also be deleted en-masse by calling <tt>Model.delete</tt> and <tt>Mo
Post.where(:category => 32).delete # => bypasses hooks
Post.where(:category => 32).destroy # => runs hooks

Please note that if <tt>Model.destroy</tt> is called, each record is deleted
separately, but <tt>Model.delete</tt> deletes all matching records with a single
Please note that if <tt>Model.destroy</tt> is called, each record is deleted
separately, but <tt>Model.delete</tt> deletes all matching records with a single
SQL query.

=== Associations
Expand Down Expand Up @@ -658,7 +658,7 @@ Associations are used in order to specify relationships between model classes th
post.add_tag(tag)
post.remove_tag(tag)
post.remove_all_tags

Note that the remove_* and remove_all_* methods do not delete the object from the database, they merely disassociate the associated object from the receiver.

All associations add a dataset method that can be used to further filter or reorder the returned objects, or modify all of them:
Expand Down Expand Up @@ -699,21 +699,21 @@ Associations can be eagerly loaded via +eager+ and the <tt>:eager</tt> associati

# eager is a dataset method, so it works with filters/orders/limits/etc.
Post.where{topic > 'M'}.order(:date).limit(5).eager(:person).all

person = Person.first
# Eager loading via :eager (will eagerly load the tags for this person's posts)
person.posts

# These are equivalent
Post.eager(:person, :tags).all
Post.eager(:person).eager(:tags).all

# Cascading via .eager
Tag.eager(:posts=>:replies).all

# Will also grab all associated posts' tags (because of :eager)
Reply.eager(:person=>:posts).all

# No depth limit (other than memory/stack), and will also grab posts' tags
# Loads all people, their posts, their posts' tags, replies to those posts,
# the person for each reply, the tag for each reply, and all posts and
Expand Down