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| -rw-r--r-- | guides/source/active_record_querying.md | 33 |
1 files changed, 28 insertions, 5 deletions
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md index f6fbc29707..2e7bb74d0b 100644 --- a/guides/source/active_record_querying.md +++ b/guides/source/active_record_querying.md @@ -1331,15 +1331,17 @@ If you want to find both by name and locked, you can chain these finders togethe Understanding The Method Chaining --------------------------------- -The ActiveRecord pattern implements [Method Chaining](http://en.wikipedia.org/wiki/Method_chaining). -This allow us to use multiple ActiveRecord methods in a simple and straightforward way. +The Active Record pattern implements [Method Chaining](http://en.wikipedia.org/wiki/Method_chaining), +which allow us to use multiple Active Record methods together in a simple and straightforward way. You can chain a method in a sentence when the previous method called returns `ActiveRecord::Relation`, like `all`, `where`, and `joins`. Methods that returns a instance of a single object (see [Retrieving a Single Object Section](#retrieving-a-single-object)) have to be be the last in the sentence. -This guide won't cover all the possibilities, just a few as example. +There are some examples below. This guide won't cover all the possibilities, just a few as example. +When a Active Record method is called, the query is not immediately generated and sent to the database, +this just happen when the data is actually needed. So each example below generate a single query. ### Retrieving filtered data from multiple tables @@ -1347,7 +1349,17 @@ This guide won't cover all the possibilities, just a few as example. Person .select('people.id, people.name, comments.text') .joins(:comments) - .where('comments.create_at > ?', 1.week.ago) + .where('comments.created_at > ?', 1.week.ago) +``` + +The result should be something like this: + +```sql +SELECT people.id, people.name, comments.text +FROM people +INNER JOIN comments + ON comments.person_id = people.id +WHERE comments.created_at = '2015-01-01' ``` ### Retrieving specific data from multiple tables @@ -1359,8 +1371,19 @@ Person .find_by('people.name' => 'John') # this should be the last ``` +The above should generate: + +```sql +SELECT people.id, people.name, companies.name +FROM people +INNER JOIN companies + ON companies.person_id = people.id +WHERE people.name = 'John' +LIMIT 1 +``` + NOTE: Remember that, if `find_by` return more than one registry, it will take just the first -and ignore the others. +and ignore the others. Note the `LIMIT 1` statement above. Find or Build a New Object -------------------------- |