MySQL 查询的影响答案

【问题标题】：Impact of MySQL QueryMySQL 查询的影响
【发布时间】：2016-10-14 16:34:20
【问题描述】：

我试图弄清楚为什么我的 MySQL 查询需要一分钟多的时间才能运行。我不知道我是否在编程效率低下，或者我是否应该期待这样的滞后时间。下面是代码。

请记住，在我搜索的大多数表（shipments、shipping_financials、shipping_consignees、shipping_shippers）中都有 10,000 到 30,000 条记录。

代码如下：

选择用户。*，COUNT(DISTINCT shippings.shipment_id) 作为 COUNT_SHIPMENTS，COUNT(DISTINCT clients.client_id) 作为 COUNT_CLIENTS，SUM(shipment_financials.shipment_financial_revenue) 作为 SUM_USER_REVENUE，SUM(shipment_financials.shipment_financial_cost) 作为 SUM_USER_COST 来自用户在 shipping.shipment_details_sales_rep = users.user_id 上加入货件左加入 shipping_financials ON shipping_financials.shipment_financial_shipment_id = shipping.shipment_id 在 clients.client_id = shipping.shipment_details_client 上加入客户加入 shipping_consignees ON shipping_consignees.shipment_consignee_shipment_id = shipping.shipment_id 加入 shipping_shippers ON shipping_shippers.shipment_shipper_shipment_id = shipping.shipment_id WHERE shipping_consignees.shipment_consignee_id = ( 选择最大（shipment_consignees.shipment_consignee_id） FROM shipping_consignees WHERE shipping.shipment_id = shipping_consignees.shipment_consignee_shipment_id ) AND shipping_shippers.shipment_shipper_id = ( 选择最小值（shipment_shippers.shipment_shipper_id） FROM shipping_shippers WHERE shipping.shipment_id = shipping_shippers.shipment_shipper_shipment_id ) AND users.user_account_id = $account_id AND shipping.shipment_voided = 0 GROUP BY users.user_id ORDER BY SUM_USER_REVENUE desc

【问题讨论】：

运行不快，因为：大量记录、5 个连接、多个相关子查询。
EXPLAIN它，做一些优化。
你使用索引吗？它将大大提高性能
@andrew - 你能解释一下索引是什么意思吗？
@BradH 在这里阅读：dev.mysql.com/doc/refman/5.7/en/mysql-indexes.html

标签： php mysql database join

【解决方案1】：

主要是 where 语句中的内联查询也减慢了查询的处理速度。但是如果这是不可避免的并且您必须使用内联查询，那么您可能会通过执行“LEFT OUTER JOIN”来减少“JOIN”的输出。

“users.*”也从表中获取全部记录，因此减慢了它的速度，但连接仍然是这里减慢查询的主要问题。

【讨论】：

【解决方案2】：

这是连接和多个查询。诀窍是将我需要的信息全部保存在一张表（出货表）中。这样我就不必加入多个表。

不是最有趣的方式来完成它，但人类确实加快了速度！

【讨论】：

这听起来不像是一个解决方案:-(

【解决方案3】：

您可以使用以下命令解释您的查询

*explain SELECT 
        users.*
        ,COUNT(DISTINCT shipments.shipment_id) as COUNT_SHIPMENTS
        ,COUNT(DISTINCT clients.client_id) as COUNT_CLIENTS
        ,SUM(shipment_financials.shipment_financial_revenue) as SUM_USER_REVENUE
        ,SUM(shipment_financials.shipment_financial_cost) as SUM_USER_COST
FROM users
JOIN shipments 
    ON shipments.shipment_details_sales_rep = users.user_id
LEFT JOIN shipment_financials 
    ON shipment_financials.shipment_financial_shipment_id = shipments.shipment_id
JOIN clients 
    ON clients.client_id = shipments.shipment_details_client
JOIN shipment_consignees 
    ON shipment_consignees.shipment_consignee_shipment_id = shipments.shipment_id
JOIN shipment_shippers 
    ON shipment_shippers.shipment_shipper_shipment_id = shipments.shipment_id
WHERE shipment_consignees.shipment_consignee_id = 
    (
        SELECT MAX(shipment_consignees.shipment_consignee_id)
        FROM shipment_consignees
        WHERE shipments.shipment_id = shipment_consignees.shipment_consignee_shipment_id
    )
AND shipment_shippers.shipment_shipper_id = 
    (
        SELECT MIN(shipment_shippers.shipment_shipper_id)
        FROM shipment_shippers
        WHERE shipments.shipment_id = shipment_shippers.shipment_shipper_shipment_id
    )
AND users.user_account_id = [TEST ACCOUNT ID]
AND shipments.shipment_voided = 0
GROUP BY users.user_id
ORDER BY SUM_USER_REVENUE desc;*

这将帮助您优化查询

【讨论】：