diff --git a/app/models/quantity.rb b/app/models/quantity.rb
index ed81124..3bc9d25 100644
--- a/app/models/quantity.rb
+++ b/app/models/quantity.rb
@@ -63,10 +63,16 @@ class Quantity < ApplicationRecord
   scope :ordered, ->(root: nil, include_root: true) {
     numbered = Arel::Table.new('numbered')
 
+    path_expr = if connection.adapter_name =~ /mysql/i
+      numbered.cast(numbered[:child_number], 'BINARY')
+    else
+      numbered[:child_number]
+    end
+
     self.model.with(numbered: numbered(:parent_id, :name)).with_recursive(arel_table.name => [
       numbered.project(
         numbered[Arel.star],
-        numbered.cast(numbered[:child_number], 'BINARY').as('path')
+        path_expr.as('path')
       ).where(numbered[root && include_root ? :id : :parent_id].eq(root)),
       numbered.project(
         numbered[Arel.star],
@@ -80,20 +86,25 @@ class Quantity < ApplicationRecord
   # be merged with :ordered
   # https://gist.github.com/ProGM/c6df08da14708dcc28b5ca325df37ceb#extending-arel
   scope :numbered, ->(parent_column, order_column) {
-    select(
-      arel_table[Arel.star],
+    row_num = Arel::Nodes::NamedFunction.new('ROW_NUMBER', [])
+      .over(Arel::Nodes::Window.new.partition(parent_column).order(order_column))
+
+    child_number = if connection.adapter_name =~ /mysql/i
       Arel::Nodes::NamedFunction.new(
         'LPAD',
         [
-          Arel::Nodes::NamedFunction.new('ROW_NUMBER', [])
-            .over(Arel::Nodes::Window.new.partition(parent_column).order(order_column)),
+          row_num,
           Arel::SelectManager.new.project(
             Arel::Nodes::NamedFunction.new('LENGTH', [Arel.star.count])
           ).from(arel_table),
           Arel::Nodes.build_quoted('0')
-        ],
-      ).as('child_number')
-    )
+        ]
+      )
+    else
+      Arel::Nodes::NamedFunction.new('format', [Arel::Nodes.build_quoted('%09d'), row_num])
+    end
+
+    select(arel_table[Arel.star], child_number.as('child_number'))
   }
 
   def to_s