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-rw-r--r--guides/source/active_record_querying.md47
1 files changed, 41 insertions, 6 deletions
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index fd1dcf22c0..cc6e08aaec 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -59,6 +59,7 @@ To retrieve objects from the database, Active Record provides several finder met
The methods are:
+* `annotate`
* `find`
* `create_with`
* `distinct`
@@ -74,11 +75,13 @@ The methods are:
* `lock`
* `none`
* `offset`
+* `optimizer_hints`
* `order`
* `preload`
* `readonly`
* `references`
* `reorder`
+* `reselect`
* `reverse_order`
* `select`
* `where`
@@ -611,7 +614,8 @@ If you want to call `order` multiple times, subsequent orders will be appended t
Client.order("orders_count ASC").order("created_at DESC")
# SELECT * FROM clients ORDER BY orders_count ASC, created_at DESC
```
-WARNING: If you are using **MySQL 5.7.5** and above, then on selecting fields from a result set using methods like `select`, `pluck` and `ids`; the `order` method will raise an `ActiveRecord::StatementInvalid` exception unless the field(s) used in `order` clause are included in the select list. See the next section for selecting fields from the result set.
+
+WARNING: In most database systems, on selecting fields with `distinct` from a result set using methods like `select`, `pluck` and `ids`; the `order` method will raise an `ActiveRecord::StatementInvalid` exception unless the field(s) used in `order` clause are included in the select list. See the next section for selecting fields from the result set.
Selecting Specific Fields
-------------------------
@@ -623,6 +627,8 @@ To select only a subset of fields from the result set, you can specify the subse
For example, to select only `viewable_by` and `locked` columns:
```ruby
+Client.select(:viewable_by, :locked)
+# OR
Client.select("viewable_by, locked")
```
@@ -805,6 +811,32 @@ SELECT * FROM articles WHERE id > 10 ORDER BY id DESC LIMIT 20
```
+### `reselect`
+
+The `reselect` method overrides an existing select statement. For example:
+
+```ruby
+Post.select(:title, :body).reselect(:created_at)
+```
+
+The SQL that would be executed:
+
+```sql
+SELECT `posts`.`created_at` FROM `posts`
+```
+
+In case the `reselect` clause is not used,
+
+```ruby
+Post.select(:title, :body).select(:created_at)
+```
+
+the SQL executed would be:
+
+```sql
+SELECT `posts`.`title`, `posts`.`body`, `posts`.`created_at` FROM `posts`
+```
+
### `reorder`
The `reorder` method overrides the default scope order. For example:
@@ -1524,7 +1556,7 @@ book.available? # => false
```
Read the full documentation about enums
-[in the Rails API docs](http://api.rubyonrails.org/classes/ActiveRecord/Enum.html).
+[in the Rails API docs](https://api.rubyonrails.org/classes/ActiveRecord/Enum.html).
Understanding The Method Chaining
---------------------------------
@@ -1702,10 +1734,13 @@ Client.find_by_sql("SELECT * FROM clients
### `select_all`
-`find_by_sql` has a close relative called `connection#select_all`. `select_all` will retrieve objects from the database using custom SQL just like `find_by_sql` but will not instantiate them. This method will return an instance of `ActiveRecord::Result` class and calling `to_hash` on this object would return you an array of hashes where each hash indicates a record.
+`find_by_sql` has a close relative called `connection#select_all`. `select_all` will retrieve
+objects from the database using custom SQL just like `find_by_sql` but will not instantiate them.
+This method will return an instance of `ActiveRecord::Result` class and calling `to_a` on this
+object would return you an array of hashes where each hash indicates a record.
```ruby
-Client.connection.select_all("SELECT first_name, created_at FROM clients WHERE id = '1'").to_hash
+Client.connection.select_all("SELECT first_name, created_at FROM clients WHERE id = '1'").to_a
# => [
# {"first_name"=>"Rafael", "created_at"=>"2012-11-10 23:23:45.281189"},
# {"first_name"=>"Eileen", "created_at"=>"2013-12-09 11:22:35.221282"}
@@ -2035,9 +2070,9 @@ under MySQL and MariaDB.
Interpretation of the output of EXPLAIN is beyond the scope of this guide. The
following pointers may be helpful:
-* SQLite3: [EXPLAIN QUERY PLAN](http://www.sqlite.org/eqp.html)
+* SQLite3: [EXPLAIN QUERY PLAN](https://www.sqlite.org/eqp.html)
-* MySQL: [EXPLAIN Output Format](http://dev.mysql.com/doc/refman/5.7/en/explain-output.html)
+* MySQL: [EXPLAIN Output Format](https://dev.mysql.com/doc/refman/5.7/en/explain-output.html)
* MariaDB: [EXPLAIN](https://mariadb.com/kb/en/mariadb/explain/)