diff --git a/lib/fluent/plugin/in_sql.rb b/lib/fluent/plugin/in_sql.rb
index 1373c97..1c7d987 100644
--- a/lib/fluent/plugin/in_sql.rb
+++ b/lib/fluent/plugin/in_sql.rb
@@ -93,7 +93,7 @@ def read_attribute_for_serialization(n)
             if v.respond_to?(:to_msgpack)
               v
             elsif v.is_a? Time
-              v.strftime('%Y-%m-%d %H:%M:%S.%6N%z')
+              v.strftime('%Y-%m-%d %H:%M:%S.%6N')
             else
               v.to_s
             end
diff --git a/lib/fluent/plugin/out_sql.rb b/lib/fluent/plugin/out_sql.rb
index e9f8ee5..5194223 100644
--- a/lib/fluent/plugin/out_sql.rb
+++ b/lib/fluent/plugin/out_sql.rb
@@ -46,6 +46,7 @@ class TableElement
 
       config_param :table, :string
       config_param :column_mapping, :string
+      config_param :primary_key, :string, :default => :id
       config_param :num_retries, :integer, :default => 5
 
       attr_reader :model
@@ -74,8 +75,10 @@ def configure(conf)
       def init(base_model)
         # See SQLInput for more details of following code
         table_name = @table
+        primary_key = @primary_key
         @model = Class.new(base_model) do
           self.table_name = table_name
+          self.primary_key = primary_key
           self.inheritance_column = '_never_use_output_'
         end