diff options
| -rw-r--r-- | guides/source/active_record_querying.textile | 64 |
1 files changed, 50 insertions, 14 deletions
diff --git a/guides/source/active_record_querying.textile b/guides/source/active_record_querying.textile index f9dbaa1125..a9cb424eaa 100644 --- a/guides/source/active_record_querying.textile +++ b/guides/source/active_record_querying.textile @@ -99,9 +99,28 @@ SELECT * FROM clients WHERE (clients.id = 10) LIMIT 1 <tt>Model.find(primary_key)</tt> will raise an +ActiveRecord::RecordNotFound+ exception if no matching record is found. +h5. +take+ + +<tt>Model.take</tt> retrieves a record without any implicit ordering. For example: + +<ruby> +client = Client.take +# => #<Client id: 1, first_name: "Lifo"> +</ruby> + +The SQL equivalent of the above is: + +<sql> +SELECT * FROM clients LIMIT 1 +</sql> + +<tt>Model.take</tt> returns +nil+ if no record is found and no exception will be raised. + +TIP: The retrieved record may vary depending on the database engine. + h5. +first+ -<tt>Model.first</tt> finds the first record matched by the supplied options, if any. For example: +<tt>Model.first</tt> finds the first record ordered by the primary key. For example: <ruby> client = Client.first @@ -111,14 +130,14 @@ client = Client.first The SQL equivalent of the above is: <sql> -SELECT * FROM clients LIMIT 1 +SELECT * FROM clients ORDER BY clients.id ASC LIMIT 1 </sql> -<tt>Model.first</tt> returns +nil+ if no matching record is found. No exception will be raised. +<tt>Model.first</tt> returns +nil+ if no matching record is found and no exception will be raised. h5. +last+ -<tt>Model.last</tt> finds the last record matched by the supplied options. For example: +<tt>Model.last</tt> finds the last record ordered by the primary key. For example: <ruby> client = Client.last @@ -131,7 +150,7 @@ The SQL equivalent of the above is: SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1 </sql> -<tt>Model.last</tt> returns +nil+ if no matching record is found. No exception will be raised. +<tt>Model.last</tt> returns +nil+ if no matching record is found and no exception will be raised. h5. +find_by+ @@ -148,12 +167,29 @@ Client.find_by first_name: 'Jon' It is equivalent to writing: <ruby> -Client.where(first_name: 'Lifo').first +Client.where(first_name: 'Lifo').take </ruby> +h5(#take_1). +take!+ + +<tt>Model.take!</tt> retrieves a record without any implicit ordering. For example: + +<ruby> +client = Client.take! +# => #<Client id: 1, first_name: "Lifo"> +</ruby> + +The SQL equivalent of the above is: + +<sql> +SELECT * FROM clients LIMIT 1 +</sql> + +<tt>Model.take!</tt> raises +ActiveRecord::RecordNotFound+ if no matching record is found. + h5(#first_1). +first!+ -<tt>Model.first!</tt> finds the first record. For example: +<tt>Model.first!</tt> finds the first record ordered by the primary key. For example: <ruby> client = Client.first! @@ -163,14 +199,14 @@ client = Client.first! The SQL equivalent of the above is: <sql> -SELECT * FROM clients LIMIT 1 +SELECT * FROM clients ORDER BY clients.id ASC LIMIT 1 </sql> -<tt>Model.first!</tt> raises +RecordNotFound+ if no matching record is found. +<tt>Model.first!</tt> raises +ActiveRecord::RecordNotFound+ if no matching record is found. h5(#last_1). +last!+ -<tt>Model.last!</tt> finds the last record. For example: +<tt>Model.last!</tt> finds the last record ordered by the primary key. For example: <ruby> client = Client.last! @@ -183,24 +219,24 @@ The SQL equivalent of the above is: SELECT * FROM clients ORDER BY clients.id DESC LIMIT 1 </sql> -<tt>Model.last!</tt> raises +RecordNotFound+ if no matching record is found. +<tt>Model.last!</tt> raises +ActiveRecord::RecordNotFound+ if no matching record is found. h5(#find_by_1). +find_by!+ -<tt>Model.find_by!</tt> finds the first record matching some conditions. It raises +RecordNotFound+ if no matching record is found. For example: +<tt>Model.find_by!</tt> finds the first record matching some conditions. It raises +ActiveRecord::RecordNotFound+ if no matching record is found. For example: <ruby> Client.find_by! first_name: 'Lifo' # => #<Client id: 1, first_name: "Lifo"> Client.find_by! first_name: 'Jon' -# => RecordNotFound +# => ActiveRecord::RecordNotFound </ruby> It is equivalent to writing: <ruby> -Client.where(first_name: 'Lifo').first! +Client.where(first_name: 'Lifo').take! </ruby> h4. Retrieving Multiple Objects |