SQL优化：内部联接

Question

假设我有下面的SQL

如何优化查询的性能？

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

我会尝试一些事情：

1. 将您的HAVING子句放入内部查询的WHERE
2. 在内部查询中选择first_name和last_name
3. 按外部查询中的first_name，last_name分组（为什么称为价格？）
4. 执行first_name ||的连接''||外部查询中的last_name

还要确保有以下索引：

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

Answer 2

通常通过创建索引来实现最佳增长。你询问内部联接。没有内部联接，它会快吗？那么你可能需要user.userid上的索引。