Merge remote-tracking branch 'upstream/master' into desc_tracker

1 files changed, 51 insertions, 1 deletions

diff --git a/railties/guides/source/active_record_querying.textile b/railties/guides/source/active_record_querying.textile
index ed3968e226..2c5d9e67e3 100644
--- a/railties/guides/source/active_record_querying.textile
+++ b/railties/guides/source/active_record_querying.textile
@@ -76,7 +76,7 @@ Primary operation of <tt>Model.find(options)</tt> can be summarized as:
 
 h4. Retrieving a Single Object
 
-Active Record lets you retrieve a single object using three different ways.
+Active Record lets you retrieve a single object using five different ways.
 
 h5. Using a Primary Key
 
@@ -130,6 +130,40 @@ SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1
 
 <tt>Model.last</tt> returns +nil+ if no matching record is found. No exception will be raised.
 
+h5. +first!+
+
+<tt>Model.first!</tt> finds the first record. For example:
+
+<ruby>
+client = Client.first!
+=> #<Client id: 1, first_name: "Lifo">
+</ruby>
+
+SQL equivalent of the above is:
+
+<sql>
+SELECT * FROM clients LIMIT 1
+</sql>
+
+<tt>Model.first!</tt> raises +RecordNotFound+ if no matching record is found.
+
+h5. +last!+
+
+<tt>Model.last!</tt> finds the last record. For example:
+
+<ruby>
+client = Client.last!
+=> #<Client id: 221, first_name: "Russel">
+</ruby>
+
+SQL equivalent of the above is:
+
+<sql>
+SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1
+</sql>
+
+<tt>Model.last!</tt> raises +RecordNotFound+ if no matching record is found.
+
 h4. Retrieving Multiple Objects
 
 h5. Using Multiple Primary Keys
@@ -747,6 +781,22 @@ h4. Specifying Conditions on Eager Loaded Associations
 
 Even though Active Record lets you specify conditions on the eager loaded associations just like +joins+, the recommended way is to use "joins":#joining-tables instead.
 
+However if you must do this, you may use +where+ as you would normally.
+
+<ruby>
+Post.includes(:comments).where("comments.visible", true)
+</ruby>
+
+This would generate a query which contains a +LEFT OUTER JOIN+ whereas the +joins+ method would generate one using the +INNER JOIN+ function instead.
+
+<ruby>
+  SELECT "posts"."id" AS t0_r0, ... "comments"."updated_at" AS t1_r5 FROM "posts" LEFT OUTER JOIN "comments" ON "comments"."post_id" = "posts"."id" WHERE (comments.visible)
+</ruby>
+
+If there was no +where+ condition, this would generate the normal set of two queries.
+
+If, in the case of this +includes+ query, there were no comments for any posts, all the posts would still be loaded. By using +joins+ (an INNER JOIN), the join conditions *must* match, otherwise no records will be returned.
+
 h3. Scopes
 
 Scoping allows you to specify commonly-used ARel queries which can be referenced as method calls on the association objects or models. With these scopes, you can use every method previously covered such as +where+, +joins+ and +includes+. All scope methods will return an +ActiveRecord::Relation+ object which will allow for further methods (such as other scopes) to be called on it.