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authorJoshua Peek <josh@joshpeek.com>2011-03-30 21:04:33 -0500
committerJoshua Peek <josh@joshpeek.com>2011-03-30 21:04:33 -0500
commit56a5da89dbcdd6d73f26f5c1be6221b684574b2b (patch)
tree577fbc16d37ed54bbda1a2a7477894caa6a7bfff /railties/guides/source/active_record_querying.textile
parent5df076ad0965dc684afff8a019fd9f92a53ada76 (diff)
parent58c3ec1b7b7ee073edf9c245de5d06426be60a25 (diff)
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Merge branch 'master' into sprockets
Conflicts: railties/lib/rails/application/configuration.rb
Diffstat (limited to 'railties/guides/source/active_record_querying.textile')
-rw-r--r--railties/guides/source/active_record_querying.textile56
1 files changed, 55 insertions, 1 deletions
diff --git a/railties/guides/source/active_record_querying.textile b/railties/guides/source/active_record_querying.textile
index 009d541106..f3a10b8b92 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
@@ -928,6 +962,26 @@ Client.exists?
The above returns +false+ if the +clients+ table is empty and +true+ otherwise.
+You can also use +any?+ and +many?+ to check for existence on a model or relation.
+
+<ruby>
+# via a model
+Post.any?
+Post.many?
+
+# via a named scope
+Post.recent.any?
+Post.recent.many?
+
+# via a relation
+Post.where(:published => true).any?
+Post.where(:published => true).many?
+
+# via an association
+Post.first.categories.any?
+Post.first.categories.many?
+</ruby>
+
h3. Calculations
This section uses count as an example method in this preamble, but the options described apply to all sub-sections.