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author | Vijay Dev <vijaydev.cse@gmail.com> | 2012-05-30 23:05:48 +0530 |
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committer | Vijay Dev <vijaydev.cse@gmail.com> | 2012-05-30 23:08:35 +0530 |
commit | 3b6d66a0c8cb631b8fadf7472bc068c9b9bf9f65 (patch) | |
tree | aaea5b309ebd3caef6509ae59eb228ed904d6ae0 /guides/source/active_record_querying.textile | |
parent | ec74763c393c6a5f54eb64f0313610aead7f815a (diff) | |
download | rails-3b6d66a0c8cb631b8fadf7472bc068c9b9bf9f65.tar.gz rails-3b6d66a0c8cb631b8fadf7472bc068c9b9bf9f65.tar.bz2 rails-3b6d66a0c8cb631b8fadf7472bc068c9b9bf9f65.zip |
Revert "Revert "[AR querying guide] Add examples for take(limit), first(limit) and last(limit)""
This reverts commit 5559a2ae98dcda6854f38890025b52edfb2836f5.
Reason: These are for selecting multiple objects and there isn't a need
to club them with the selecting single objects section, as discussed
with the author.
Diffstat (limited to 'guides/source/active_record_querying.textile')
-rw-r--r-- | guides/source/active_record_querying.textile | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/guides/source/active_record_querying.textile b/guides/source/active_record_querying.textile index 294ef25b33..eceeb814fd 100644 --- a/guides/source/active_record_querying.textile +++ b/guides/source/active_record_querying.textile @@ -259,6 +259,54 @@ SELECT * FROM clients WHERE (clients.id IN (1,10)) WARNING: <tt>Model.find(array_of_primary_key)</tt> will raise an +ActiveRecord::RecordNotFound+ exception unless a matching record is found for <strong>all</strong> of the supplied primary keys. +h5. take + +<tt>Model.take(limit)</tt> retrieves the first number of records specified by +limit+ without any explicit ordering: + +<ruby> +Client.take(2) +# => [#<Client id: 1, first_name: "Lifo">, + #<Client id: 2, first_name: "Raf">] +</ruby> + +The SQL equivalent of the above is: + +<sql> +SELECT * FROM clients LIMIT 2 +</sql> + +h5. first + +<tt>Model.first(limit)</tt> finds the first number of records specified by +limit+ ordered by primary key: + +<ruby> +Client.first(2) +# => [#<Client id: 1, first_name: "Lifo">, + #<Client id: 2, first_name: "Raf">] +</ruby> + +The SQL equivalent of the above is: + +<sql> +SELECT * FROM clients LIMIT 2 +</sql> + +h5. last + +<tt>Model.last(limit)</tt> finds the number of records specified by +limit+ ordered by primary key in descending order: + +<ruby> +Client.last(2) +# => [#<Client id: 10, first_name: "Ryan">, + #<Client id: 9, first_name: "John">] +</ruby> + +The SQL equivalent of the above is: + +<sql> +SELECT * FROM clients ORDER By id DESC LIMIT 2 +</sql> + h4. Retrieving Multiple Objects in Batches We often need to iterate over a large set of records, as when we send a newsletter to a large set of users, or when we export data. |