SQL優化：內部連接

Question

假設我已經得到下面的SQL

如何優化查詢的性能？

select product, address, quantity, 
    price, create_date, sum(no_of_photo) as no_of_photo 
from 
(
    SELECT customer.PROJECT_ID as project_id , 
     customer.ORDER_TYPE as order_type, 
     customer.product_name as product, 
     customer.address_name as address ,  
     customer.quantity_name as quantity, 
     user.first_name || ' ' || user.last_name AS price, 
     customer.create_date, customer.no_of_photo 
    FROM customer 
    INNER JOIN user 
     ON customer.creation_userid = user.userid 
) master_list 
group by project_id, order_type , 
    product, address, quantity, price, 
    create_date 
having project_id = 123456 
order by product, address, quantity, price, create_date 

Answer 1

一對夫婦的事情，我會嘗試：

1. 把你的HAVING子句爲WHERE在內部查詢
2. SELECT名字，並在內部查詢
3. 集團通過自己的姓氏first_name，last_name在外部查詢中（爲什麼叫做價格？）
4. 是否連接first_name || ''||姓氏在外部查詢

也能確保有指標上：

• customer.project_id
• customer.creation_userid
• user.userid

Answer 2

最好的增加通常通過自帶創建一個索引。你詢問內部連接。沒有內部連接，它快嗎？那麼你可能需要user.userid上的索引。