diff --git a/CHANGELOG.md b/CHANGELOG.md
index 423cb971a..cda67f6b5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@
 - [#763](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/763) Refactor columns introspection query to make it faster
 - [#783](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/783) Update test matrix
 - [#820](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/820) Enable frozen strings for tests
+- [#821](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/821) Enable frozen strings - part 1
 
 #### Added
 
diff --git a/Rakefile b/Rakefile
index 79a4a5885..1477ac6f5 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'bundler/gem_tasks'
 require 'rake/testtask'
 require_relative 'test/support/paths_sqlserver'
diff --git a/lib/active_record/connection_adapters/sqlserver/core_ext/active_record.rb b/lib/active_record/connection_adapters/sqlserver/core_ext/active_record.rb
index ae8359686..03849a5cb 100644
--- a/lib/active_record/connection_adapters/sqlserver/core_ext/active_record.rb
+++ b/lib/active_record/connection_adapters/sqlserver/core_ext/active_record.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLServer
diff --git a/lib/active_record/connection_adapters/sqlserver/core_ext/attribute_methods.rb b/lib/active_record/connection_adapters/sqlserver/core_ext/attribute_methods.rb
index 6687ac36a..815da2914 100644
--- a/lib/active_record/connection_adapters/sqlserver/core_ext/attribute_methods.rb
+++ b/lib/active_record/connection_adapters/sqlserver/core_ext/attribute_methods.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'active_record/attribute_methods'
 
 module ActiveRecord
diff --git a/lib/active_record/connection_adapters/sqlserver/core_ext/calculations.rb b/lib/active_record/connection_adapters/sqlserver/core_ext/calculations.rb
index d2b7096c7..c17d77876 100644
--- a/lib/active_record/connection_adapters/sqlserver/core_ext/calculations.rb
+++ b/lib/active_record/connection_adapters/sqlserver/core_ext/calculations.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'active_record/relation'
 require 'active_record/version'
 
diff --git a/lib/active_record/connection_adapters/sqlserver/core_ext/explain.rb b/lib/active_record/connection_adapters/sqlserver/core_ext/explain.rb
index baa8d736c..76e1eb7a8 100644
--- a/lib/active_record/connection_adapters/sqlserver/core_ext/explain.rb
+++ b/lib/active_record/connection_adapters/sqlserver/core_ext/explain.rb
@@ -1,10 +1,12 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLServer
       module CoreExt
         module Explain
 
-          SQLSERVER_STATEMENT_PREFIX = 'EXEC sp_executesql '.freeze
+          SQLSERVER_STATEMENT_PREFIX = 'EXEC sp_executesql '
           SQLSERVER_STATEMENT_REGEXP = /N'(.+)', N'(.+)', (.+)/
 
           def exec_explain(queries)
diff --git a/lib/active_record/connection_adapters/sqlserver/core_ext/explain_subscriber.rb b/lib/active_record/connection_adapters/sqlserver/core_ext/explain_subscriber.rb
index 45c56cd78..712465543 100644
--- a/lib/active_record/connection_adapters/sqlserver/core_ext/explain_subscriber.rb
+++ b/lib/active_record/connection_adapters/sqlserver/core_ext/explain_subscriber.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 ActiveSupport.on_load(:active_record) do
   silence_warnings do
     # Already defined in Rails
diff --git a/lib/active_record/connection_adapters/sqlserver/core_ext/finder_methods.rb b/lib/active_record/connection_adapters/sqlserver/core_ext/finder_methods.rb
index 519628a22..7db8aaecc 100644
--- a/lib/active_record/connection_adapters/sqlserver/core_ext/finder_methods.rb
+++ b/lib/active_record/connection_adapters/sqlserver/core_ext/finder_methods.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'active_record/relation'
 require 'active_record/version'
 
diff --git a/lib/active_record/connection_adapters/sqlserver/core_ext/preloader.rb b/lib/active_record/connection_adapters/sqlserver/core_ext/preloader.rb
index 5fca92532..0171f4c65 100644
--- a/lib/active_record/connection_adapters/sqlserver/core_ext/preloader.rb
+++ b/lib/active_record/connection_adapters/sqlserver/core_ext/preloader.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_record/associations/preloader"
 
 module ActiveRecord
diff --git a/lib/active_record/connection_adapters/sqlserver/core_ext/query_methods.rb b/lib/active_record/connection_adapters/sqlserver/core_ext/query_methods.rb
index 91d17721f..31ed4fa79 100644
--- a/lib/active_record/connection_adapters/sqlserver/core_ext/query_methods.rb
+++ b/lib/active_record/connection_adapters/sqlserver/core_ext/query_methods.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'active_record/relation'
 require 'active_record/version'
 
diff --git a/lib/active_record/connection_adapters/sqlserver/showplan/printer_table.rb b/lib/active_record/connection_adapters/sqlserver/showplan/printer_table.rb
index 70de897db..4885d74cc 100644
--- a/lib/active_record/connection_adapters/sqlserver/showplan/printer_table.rb
+++ b/lib/active_record/connection_adapters/sqlserver/showplan/printer_table.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLServer
diff --git a/lib/active_record/connection_adapters/sqlserver/showplan/printer_xml.rb b/lib/active_record/connection_adapters/sqlserver/showplan/printer_xml.rb
index f620a6453..00c268143 100644
--- a/lib/active_record/connection_adapters/sqlserver/showplan/printer_xml.rb
+++ b/lib/active_record/connection_adapters/sqlserver/showplan/printer_xml.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ActiveRecord
   module ConnectionAdapters
     module SQLServer
diff --git a/test/cases/column_test_sqlserver.rb b/test/cases/column_test_sqlserver.rb
index c5b6ef0a1..8d74c2908 100644
--- a/test/cases/column_test_sqlserver.rb
+++ b/test/cases/column_test_sqlserver.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-# encoding: UTF-8
 require 'cases/helper_sqlserver'
 
 class ColumnTestSQLServer < ActiveRecord::TestCase
diff --git a/test/cases/transaction_test_sqlserver.rb b/test/cases/transaction_test_sqlserver.rb
index edac70ca3..f94694e36 100644
--- a/test/cases/transaction_test_sqlserver.rb
+++ b/test/cases/transaction_test_sqlserver.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-# encoding: UTF-8
 require 'cases/helper_sqlserver'
 require 'models/ship'
 require 'models/developer'
diff --git a/test/cases/trigger_test_sqlserver.rb b/test/cases/trigger_test_sqlserver.rb
index 1e9e0e979..88ccf157e 100644
--- a/test/cases/trigger_test_sqlserver.rb
+++ b/test/cases/trigger_test_sqlserver.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-# encoding: UTF-8
 require 'cases/helper_sqlserver'
 
 class SQLServerTriggerTest < ActiveRecord::TestCase
diff --git a/test/cases/uuid_test_sqlserver.rb b/test/cases/uuid_test_sqlserver.rb
index 3c4947f18..4a96c29ce 100644
--- a/test/cases/uuid_test_sqlserver.rb
+++ b/test/cases/uuid_test_sqlserver.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-# encoding: UTF-8
 require 'cases/helper_sqlserver'
 
 class SQLServerUuidTest < ActiveRecord::TestCase