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Diffstat (limited to 'guides/source/active_record_querying.md')
| -rw-r--r-- | guides/source/active_record_querying.md | 46 |
1 files changed, 24 insertions, 22 deletions
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md index af15d4870c..e9f6275e55 100644 --- a/guides/source/active_record_querying.md +++ b/guides/source/active_record_querying.md @@ -50,7 +50,7 @@ class Role < ApplicationRecord end ``` -Active Record will perform queries on the database for you and is compatible with most database systems (MySQL, PostgreSQL and SQLite to name a few). Regardless of which database system you're using, the Active Record method format will always be the same. +Active Record will perform queries on the database for you and is compatible with most database systems, including MySQL, MariaDB, PostgreSQL and SQLite. Regardless of which database system you're using, the Active Record method format will always be the same. Retrieving Objects from the Database ------------------------------------ @@ -153,9 +153,9 @@ You can pass in a numerical argument to the `take` method to return up to that n ```ruby client = Client.take(2) # => [ - #<Client id: 1, first_name: "Lifo">, - #<Client id: 220, first_name: "Sara"> -] +# #<Client id: 1, first_name: "Lifo">, +# #<Client id: 220, first_name: "Sara"> +# ] ``` The SQL equivalent of the above is: @@ -192,10 +192,10 @@ You can pass in a numerical argument to the `first` method to return up to that ```ruby client = Client.first(3) # => [ - #<Client id: 1, first_name: "Lifo">, - #<Client id: 2, first_name: "Fifo">, - #<Client id: 3, first_name: "Filo"> -] +# #<Client id: 1, first_name: "Lifo">, +# #<Client id: 2, first_name: "Fifo">, +# #<Client id: 3, first_name: "Filo"> +# ] ``` The SQL equivalent of the above is: @@ -243,10 +243,10 @@ You can pass in a numerical argument to the `last` method to return up to that n ```ruby client = Client.last(3) # => [ - #<Client id: 219, first_name: "James">, - #<Client id: 220, first_name: "Sara">, - #<Client id: 221, first_name: "Russel"> -] +# #<Client id: 219, first_name: "James">, +# #<Client id: 220, first_name: "Sara">, +# #<Client id: 221, first_name: "Russel"> +# ] ``` The SQL equivalent of the above is: @@ -1613,7 +1613,7 @@ now want the client named 'Nick': ```ruby nick = Client.find_or_initialize_by(first_name: 'Nick') -# => <Client id: nil, first_name: "Nick", orders_count: 0, locked: true, created_at: "2011-08-30 06:09:27", updated_at: "2011-08-30 06:09:27"> +# => #<Client id: nil, first_name: "Nick", orders_count: 0, locked: true, created_at: "2011-08-30 06:09:27", updated_at: "2011-08-30 06:09:27"> nick.persisted? # => false @@ -1645,10 +1645,10 @@ Client.find_by_sql("SELECT * FROM clients INNER JOIN orders ON clients.id = orders.client_id ORDER BY clients.created_at desc") # => [ - #<Client id: 1, first_name: "Lucas" >, - #<Client id: 2, first_name: "Jan" >, - # ... -] +# #<Client id: 1, first_name: "Lucas" >, +# #<Client id: 2, first_name: "Jan" >, +# ... +# ] ``` `find_by_sql` provides you with a simple way of making custom calls to the database and retrieving instantiated objects. @@ -1660,9 +1660,9 @@ Client.find_by_sql("SELECT * FROM clients ```ruby Client.connection.select_all("SELECT first_name, created_at FROM clients WHERE id = '1'") # => [ - {"first_name"=>"Rafael", "created_at"=>"2012-11-10 23:23:45.281189"}, - {"first_name"=>"Eileen", "created_at"=>"2013-12-09 11:22:35.221282"} -] +# {"first_name"=>"Rafael", "created_at"=>"2012-11-10 23:23:45.281189"}, +# {"first_name"=>"Eileen", "created_at"=>"2013-12-09 11:22:35.221282"} +# ] ``` ### `pluck` @@ -1915,7 +1915,7 @@ EXPLAIN for: SELECT `users`.* FROM `users` INNER JOIN `articles` ON `articles`.` 2 rows in set (0.00 sec) ``` -under MySQL. +under MySQL and MariaDB. Active Record performs a pretty printing that emulates that of the corresponding database shell. So, the same query running with the @@ -1975,7 +1975,7 @@ EXPLAIN for: SELECT `articles`.* FROM `articles` WHERE `articles`.`user_id` IN 1 row in set (0.00 sec) ``` -under MySQL. +under MySQL and MariaDB. ### Interpreting EXPLAIN @@ -1986,4 +1986,6 @@ following pointers may be helpful: * MySQL: [EXPLAIN Output Format](http://dev.mysql.com/doc/refman/5.7/en/explain-output.html) +* MariaDB: [EXPLAIN](https://mariadb.com/kb/en/mariadb/explain/) + * PostgreSQL: [Using EXPLAIN](http://www.postgresql.org/docs/current/static/using-explain.html) |