MySQL Row Numbering not getting desired results

Question

I have the below query and what I would like to do is add a column that will identify what order this is for a distinct customer. entity_id is unique per order, so really all I want to do is number unique entity_id for each customer ordered by created_at. The problem is that there is a row for every item in a order so it is numbering it wrong with my current query.

This is the current results

 Order Date          ,OrderID, SKU ,Qty     ,Customer Email   ,First,last  ,seqnum
'2015-04-01 14:48:13','19406','201','2.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','201','2.0000','test@google.com','joe','vers','2'
'2015-04-01 14:48:13','19406','201','2.0000','test@google.com','joe','vers','3'
'2015-04-01 14:48:13','19406','201','2.0000','test@google.com','joe','vers','4'
'2015-04-01 14:48:13','19406','201','2.0000','test@google.com','joe','vers','5'
'2015-04-01 14:48:13','19406','103','1.0000','test@google.com','joe','vers','6'
'2015-04-01 14:48:13','19406','102','1.0000','test@google.com','joe','vers','7'
'2015-04-01 14:48:13','19406','102','1.0000','test@google.com','joe','vers','8'
'2015-04-01 14:48:13','19406','102','1.0000','test@google.com','joe','vers','9'
'2015-04-01 14:48:13','19406','201','1.0000','test@google.com','joe','vers','10'
'2015-04-01 14:48:13','19406','102','1.0000','test@google.com','joe','vers','11'
'2015-04-01 14:48:13','19406','105','1.0000','test@google.com','joe','vers','12'
'2015-04-13 17:45:15','20537','105','1.0000','test@google.com','joe','vers','13'
'2015-04-13 17:45:15','20537','102','1.0000','test@google.com','joe','vers','14'
'2015-04-13 17:45:15','20537','201','1.0000','test@google.com','joe','vers','15'
'2015-04-13 17:45:15','20537','201','1.0000','test@google.com','joe','vers','16'
'2015-04-29 14:42:28','22212','102','1.0000','test@google.com','joe','vers','17'
'2015-05-11 17:11:22','23301','102','1.0000','test@google.com','joe','vers','18'

This is the desired results

 Order Date          ,OrderID, SKU ,Qty     ,Customer Email   ,First,last  ,seqnum
'2015-04-01 14:48:13','19406','201','2.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','201','2.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','201','2.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','201','2.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','201','2.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','103','1.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','102','1.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','102','1.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','102','1.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','201','1.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','102','1.0000','test@google.com','joe','vers','1'
'2015-04-01 14:48:13','19406','105','1.0000','test@google.com','joe','vers','1'
'2015-04-13 17:45:15','20537','105','1.0000','test@google.com','joe','vers','2'
'2015-04-13 17:45:15','20537','102','1.0000','test@google.com','joe','vers','2'
'2015-04-13 17:45:15','20537','201','1.0000','test@google.com','joe','vers','2'
'2015-04-13 17:45:15','20537','201','1.0000','test@google.com','joe','vers','2'
'2015-04-29 14:42:28','22212','102','1.0000','test@google.com','joe','vers','3'
'2015-05-11 17:11:22','23301','102','1.0000','test@google.com','joe','vers','4'

This is the query:

select sfo.created_at AS "Order Date", sfo.entity_id AS "Order ID",
       left(sfoi.sku,3) AS "SKU", sfoi.qty_ordered,   
       sfo.customer_email AS "Customer Email",     
       sfo.customer_firstname AS "Customer Firstname",     
       sfo.Customer_lastname AS "Customer Lastname",
       (@rn := if(@e = sfo.customer_email, @rn + 1,
                  if(@e := sfo.customer_email, 1, 1)
                 )
       ) as seqnum
from sales_flat_order sfo join
     sales_flat_order_item sfoi
     on sfoi.order_id = sfo.entity_id join
     sales_flat_order_address sfoa        
     on sfoa.entity_id = sfo.billing_address_id cross join
     (select @rn := 0, @e := '') params
order by sfo.customer_email, created_at;

Answer 1

Ah, I see. The orders are numbers based on the email . Okay.

select sfo.created_at AS "Order Date", sfo.entity_id AS "Order ID",
       left(sfoi.sku,3) AS "SKU", sfoi.qty_ordered,   
       sfo.customer_email AS "Customer Email",     
       sfo.customer_firstname AS "Customer Firstname",     
       sfo.Customer_lastname AS "Customer Lastname",
       (@rn := if(@e = sfo.customer_email,
                  if(@o = sfo.entity_id, @rn,
                     if(@o := sfo.entity_id, @rn + 1, @rn + 1
                       )
                    ),
                  if(@e := sfo.customer_email,
                     if(@o := sfo.entity_id, 1, 1),
                     if(@o := sfo.entity_id, 1, 1)
                    )
                 )
       ) as seqnum
from sales_flat_order sfo join
     sales_flat_order_item sfoi
     on sfoi.order_id = sfo.entity_id join
     sales_flat_order_address sfoa        
     on sfoa.entity_id = sfo.billing_address_id cross join
     (select @rn := 0, @e := '', @o := -1) params
order by sfo.customer_email, created_at, orderid;

This assumes that created_at is the same for each order.