Reverse order of values when upserting

CHANGELOG.md

@@ -1,3 +1,9 @@
+## Unreleased
+
+#### Fixed
+
+- [#1318](https://github.com/rails-sqlserver/activerecord-sqlserver-adapter/pull/1318) Reverse order of values when upserting
+
 ## v8.0.5
 
 #### Added

lib/active_record/connection_adapters/sqlserver/database_statements.rb

@@ -159,6 +159,8 @@ def build_insert_sql(insert) # :nodoc:
 
 
         def build_sql_for_merge_insert(insert:, insert_all:, columns_with_uniqueness_constraints:) # :nodoc:
+          insert_all.inserts.reverse! if insert.update_duplicates?
+
           sql = <<~SQL
             MERGE INTO #{insert.model.quoted_table_name} WITH (UPDLOCK, HOLDLOCK) AS target
             USING (

test/cases/insert_all_test_sqlserver.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require "cases/helper_sqlserver"
+require "models/book"
+
+class InsertAllTestSQLServer < ActiveRecord::TestCase
+  # Test ported from the Rails `main` branch that is not on the `8-0-stable` branch.
+  def test_insert_all_only_applies_last_value_when_given_duplicate_identifiers
+    skip unless supports_insert_on_duplicate_skip?
+
+    Book.insert_all [
+                      { id: 111, name: "expected_new_name" },
+                      { id: 111, name: "unexpected_new_name" }
+                    ]
+    assert_equal "expected_new_name", Book.find(111).name
+  end
+
+  # Test ported from the Rails `main` branch that is not on the `8-0-stable` branch.
+  def test_upsert_all_only_applies_last_value_when_given_duplicate_identifiers
+    skip unless supports_insert_on_duplicate_update? && !current_adapter?(:PostgreSQLAdapter)
+
+    Book.create!(id: 112, name: "original_name")
+
+    Book.upsert_all [
+                      { id: 112, name: "unexpected_new_name" },
+                      { id: 112, name: "expected_new_name" }
+                    ]
+    assert_equal "expected_new_name", Book.find(112).name
+  end
+end