Add ActiveRecord Query For This Or That as a rails til

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_815 TILs and counting..._
+_816 TILs and counting..._
 
 ---
 
@@ -476,6 +476,7 @@ _815 TILs and counting..._
 
 - [Add React With Webpacker To A New Rails App](rails/add-react-with-webpacker-to-a-new-rails-app.md)
 - [Access Secrets In A Rails 5.2 App](rails/access-secrets-in-a-rails-5-2-app.md)
+- [ActiveRecord Query For This Or That](rails/active-record-query-for-this-or-that.md)
 - [Advance The Date](rails/advance-the-date.md)
 - [All or Nothing Database Transactions](rails/all-or-nothing-database-transactions.md)
 - [Attach A File With Capybara](rails/attach-a-file-with-capybara.md)

rails/active-record-query-for-this-or-that.md

@@ -0,0 +1,26 @@
+# ActiveRecord Query For This Or That
+
+When including multiple `where` clauses on a query, we are adding more
+specificity to the resulting `ActiveRecord` relation -- it's like saying we
+want records that match this _and_ that. But what about when we want to find
+records that match this _or_ that?
+
+This is supported by `ActiveRecord` through the `or` query method.
+
+Let's say we want all books that are either unpublished _or_ are published in
+2019.
+
+```ruby
+> Book.where(status: 'unpublished').or(Book.where(publication_year: 2019))
+=> #<ActiveRecord::Relation [...]>
+```
+
+This will generate SQL that includes a `where` clause like the following:
+
+```sql
+where (books.status = 'unpublished' or books.publication_year = 2019)
+```
+
+See the
+[docs](https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-or)
+for more details.