php - MySQL 查询的影响

Question

我想弄清楚为什么我的 MySQL 查询需要一分钟多的时间才能运行。我不知道我是否正在低效地编程，或者我是否应该期待这样的滞后时间。下面是代码。

请记住，在我搜索的大部分表格(shipments、shipment_financials、shipment_consignees、shipment_shippers)中有 10,000 到 30,000 条记录。

代码如下:

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 = $account_id
    AND shipments.shipment_voided = 0
GROUP BY users.user_id
ORDER BY SUM_USER_REVENUE desc

Answer 1

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

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