Gerar uma tabela de pedidos agrupados por user_id que soma a quantidade do produto

select p.user_id,
       max( CASE WHEN pm.meta_key = '_billing_first_name' and p.ID = pm.post_id THEN pm.meta_value END ) as _billing_first_name,
       max( CASE WHEN pm.meta_key = '_billing_last_name' and p.ID = pm.post_id THEN pm.meta_value END ) as _billing_last_name,
       max( CASE WHEN pm.meta_key = '_billing_address_1' and p.ID = pm.post_id THEN pm.meta_value END ) as _billing_address_1,
       group_concat(distinct oi.order_item_name separator '|' ) as order_items
from wp_posts p join
     wp_postmeta pm
     on p.ID = pm.post_id join
     wp_woocommerce_order_items oi
     on p.ID = oi.order_id
where p.post_type = 'shop_order' and
      p.post_status = 'wc-completed' and
      oi.order_item_name = 'Product Name'
group by p.user_id;