2 files changed, 40 insertions, 0 deletions
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index ee8cf4ade6..673dcfc1d3 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -659,6 +659,23 @@ FROM orders
 GROUP BY date(created_at)
 ```
 
+### Total of grouped items
+
+To get the total of grouped items on a single query call `count` after the `group`.
+
+```ruby
+Order.group(:status).count
+# => { 'awaiting_approval' => 7, 'paid' => 12 }
+```
+
+The SQL that would be executed would be something like this:
+
+```sql
+SELECT COUNT (*) AS count_all, status AS status
+FROM "orders"
+GROUP BY status
+```
+
 Having
 ------
 
diff --git a/guides/source/migrations.md b/guides/source/migrations.md
index 6742c05946..31e314c69b 100644
--- a/guides/source/migrations.md
+++ b/guides/source/migrations.md
@@ -415,6 +415,29 @@ end
 removes the `description` and `name` columns, creates a `part_number` string
 column and adds an index on it. Finally it renames the `upccode` column.
 
+### Changing Columns
+
+Like the `remove_column` and `add_column` Rails provides the `change_column`
+migration method.
+
+```ruby
+change_column :products, :part_number, :text
+```
+
+This changes the column `part_number` on products table to be a `:text` field.
+
+Besides `change_column`, the `change_column_null` and `change_column_default`
+methods are used specifically to change the null and default values of a
+column.
+
+```ruby
+change_column_null :products, :name, false
+change_column_default :products, :approved, false
+```
+
+This sets `:name` field on products to a `NOT NULL` column and the default
+value of the `:approved` field to false.
+
 ### When Helpers aren't Enough
 
 If the helpers provided by Active Record aren't enough you can use the `execute`