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Diffstat (limited to 'guides/source/active_record_querying.md')
| -rw-r--r-- | guides/source/active_record_querying.md | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md index 9d349691b4..9a13e3bda7 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 ------------------------------------ @@ -472,6 +472,12 @@ NOTE: Only equality, range and subset checking are possible with Hash conditions Client.where(locked: true) ``` +This will generate SQL like this: + +```sql +SELECT * FROM clients WHERE (clients.locked = 1) +``` + The field name can also be a string: ```ruby @@ -517,13 +523,17 @@ SELECT * FROM clients WHERE (clients.orders_count IN (1,3,5)) ### NOT Conditions -`NOT` SQL queries can be built by `where.not`. +`NOT` SQL queries can be built by `where.not`: ```ruby -Article.where.not(author: author) +Client.where.not(locked: true) ``` -In other words, this query can be generated by calling `where` with no argument, then immediately chain with `not` passing `where` conditions. +In other words, this query can be generated by calling `where` with no argument, then immediately chain with `not` passing `where` conditions. This will generate SQL like this: + +```sql +SELECT * FROM clients WHERE (clients.locked != 1) +``` Ordering -------- @@ -1915,7 +1925,7 @@ 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 +1985,7 @@ 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 +1996,6 @@ 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) |