Add Scope Records To A Lower Or Upper Bound as a Rails TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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@@ -1126,6 +1126,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Run Some Code Whenever Rails Console Starts](rails/run-some-code-whenever-rails-console-starts.md)
 - [Scaffold Auth Functionality With Rails 8 Generator](rails/scaffold-auth-functionality-with-rails-8-generator.md)
 - [Schedule Sidekiq Jobs Out Into The Future](rails/schedule-sidekiq-jobs-out-into-the-future.md)
+- [Scope Records To A Lower Or Upper Bound](rails/scope-records-to-a-lower-or-upper-bound.md)
 - [Secure Passwords With Rails And Bcrypt](rails/secure-passwords-with-rails-and-bcrypt.md)
 - [Select A Select By Selector](rails/select-a-select-by-selector.md)
 - [Select A Specific Rails Version To Install](rails/select-a-specific-rails-version-to-install.md)

rails/scope-records-to-a-lower-or-upper-bound.md

@@ -0,0 +1,55 @@
+# Scope Records To A Lower Or Upper Bound
+
+Typically when we use
+[`#where`](https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-where)
+to scope queries against ActiveRecord models, we are looking to do a direct
+"equals" comparison.
+
+Such as `auth_codes.user_id = 1` in the example below.
+
+```ruby
+> AuthCode.where(user_id: 1)
+  AuthCode Load (0.4ms)  SELECT "auth_codes".* FROM "auth_codes" WHERE "auth_codes"."user_id" = 1 /* loading for pp */ LIMIT 11
+```
+
+We can do more powerful things with `#where` (assuming your database supports
+it, in my case PostgreSQL), such as comparing over ranges of dates. Ruby's
+range syntax gives us an elegant way to express ranges.
+
+```ruby
+> 2..10 # range with lower bound of 2 and upper bound of 10
+
+> 2.. # 'end'less range
+
+> ..10 # 'begin'less range
+```
+
+These latter two examples are ranges that are unbounded on one side or the
+other. We can use these in ActiveRecord `#where` queries to do "greater than or
+equal to" and "less than or equal to" conditionals.
+
+And we can do the same with ranges of dates like in the following queries.
+
+
+```ruby
+> AuthCode.where(created_at: 10.days.ago..).count
+  AuthCode Count (97.1ms)  SELECT COUNT(*) FROM "auth_codes" WHERE "auth_codes"."created_at" >= '2025-09-24 00:35:46.937715'
+
+> AuthCode.where(created_at: 10.days.ago..5.days.ago).count
+  AuthCode Count (0.6ms)  SELECT COUNT(*) FROM "auth_codes" WHERE "auth_codes"."created_at" BETWEEN '2025-09-24 00:35:59.901441' AND '2025-09-29 00:35:59.901512'
+
+> AuthCode.where(created_at: ..5.days.ago).count
+  AuthCode Count (0.3ms)  SELECT COUNT(*) FROM "auth_codes" WHERE "auth_codes"."created_at" <= '2025-09-29 00:36:09.731444'
+```
+
+Notice in the generated SQL how the simple `#where` method gets transformed
+into a `>=`, a `<=`, or a `between` clause.
+
+And while dates are a powerful example of this, there is nothing to stop us
+from querying against other kinds of ranges like numeric ones.
+
+```ruby
+# Orders under $10
+ten_dollars_in_cents = 10 * 100
+Order.where.not(fulfilled_at: nil).where(amount: ..ten_dollars_in_cents)
+```