如何優化和加速當前的Magento SQL查詢？

Question

如何優化當前的Magento SQL查詢？

SELECT​ ​ customer_entity.email,​ ​ COUNT(sales_flat_order.increment_id)
AS​ ​ number_of_orders
FROM​ ​ customer_entity
LEFT JOIN​ ​ sales_flat_order​ ​ ON​ ​ sales_flat_order.customer_email​ ​ =
customer_entity.email
GROUP​ ​ BY​ ​ customer_entity.email
ORDER​ ​ BY​ ​ number_of_orders​ ​ DESC;

Answer 1

如果同一表中存在customer_email，為什么還要進行Join？

SELECT `customer_email`, COUNT(increment_id) as number_of_orders 
FROM `sales_flat_order` 
GROUP BY customer_email 
ORDER BY number_of_orders DESC;