Question

在我的查询中添加ORDER BY时遇到问题。没有ORDER BY查询需要大约26ms，只要我添加一个ORDER BY就会花费20s。

我尝试过几种不同的方式，但似乎可以减少时间。

尝试

FORCE INDEX (PRIMARY)

试图包裹

SELECT * FROM (...)

有没有人有其他想法？

QUERY：

    SELECT 
    orders.id AS order_number, 
    orders.created AS order_created, 
    CONCAT_WS(' ', clients.name, office.name) AS client_office, 
    order_item.code AS product_code, 
    order_item.name AS product_name, 
    order_item.description AS product_description, 
    order_item.sale_price, 
    jobs.rating AS job_rating, 
    job_role.start_booking AS book_start, 
    job_role.end_booking AS book_end, 
    CONCAT_WS(' ', admin_staffs.first_name, admin_staffs.last_name) AS soul, 
    admin_roles.name AS role, 
    services.name AS service, 
    COUNT(job_item.id) AS total_assets, 
    COALESCE(orders.project_name, CONCAT_WS(' ', orders.location_unit_no, orders.location_street_number, orders.location_street_number, orders.location_street_name
                )
            ) AS order_title
FROM jobs
LEFT JOIN job_item ON jobs.id = job_item.job_id
LEFT JOIN job_role ON jobs.id = job_role.job_id
LEFT JOIN admin_roles ON admin_roles.id = job_role.role_id
LEFT JOIN services ON services.id = jobs.service_id
LEFT JOIN admin_staffs ON admin_staffs.id = job_role.staff_id
LEFT JOIN order_item ON jobs.item_id = order_item.id
LEFT JOIN orders ON orders.id = order_item.order_id
LEFT JOIN clients ON orders.client_id = clients.id
LEFT JOIN office ON orders.office_id = office.id
LEFT JOIN client_users ON orders.user_id = client_users.id
GROUP BY jobs.id
ORDER BY jobs.order_id DESC
LIMIT 50

说明：


+----+-------------+--------------+--------+----------------+-----------+---------+--------------------------------------+-------+---------------------------------+
| id | select_type | table        | type   | possible_keys  | key       | key_len | ref                                  | rows  | Extra                           |
+----+-------------+--------------+--------+----------------+-----------+---------+--------------------------------------+-------+---------------------------------+
| 1  |    SIMPLE   | jobs         | ALL    | PRIMARY        | NULL      | NULL    | NULL                                 | 49555 | Using temporary; Using filesort |        
| 1  |    SIMPLE   | job_item     | ref    | job_id         | job_id    | 5       | Wx3392vf_UCO_app.jobs.id             | 8     | Using where; Using index        |
| 1  |    SIMPLE   | job_role     | ref    | job_id         | job_id    | 4       | Wx3392vf_UCO_app.jobs.id             | 1     | Using where                     |
| 1  |    SIMPLE   | admin_roles  | eq_ref | PRIMARY        | PRIMARY   | 4       | Wx3392vf_UCO_app.job_role.role_id    | 1     | Using where                     |
| 1  |    SIMPLE   | services     | eq_ref | PRIMARY        | PRIMARY   | 4       | Wx3392vf_UCO_app.jobs.service_id     | 1     | Using where                     |
| 1  |    SIMPLE   | admin_staffs | eq_ref | PRIMARY        | PRIMARY   | 4       | Wx3392vf_UCO_app.job_role.staff_id   | 1     | NULL                            |    
| 1  |    SIMPLE   | order_item   | eq_ref | PRIMARY        | PRIMARY   | 4       | Wx3392vf_UCO_app.jobs.item_id        | 1     | Using where                     |
| 1  |    SIMPLE   | orders       | eq_ref | PRIMARY        | PRIMARY   | 4       | Wx3392vf_UCO_app.order_item.order_id | 1     | Using where                     |
| 1  |    SIMPLE   | clients      | eq_ref | PRIMARY        | PRIMARY   | 4       | Wx3392vf_UCO_app.orders.client_id    | 1     | Using where                     |
| 1  |    SIMPLE   | office       | eq_ref | PRIMARY        | PRIMARY   | 4       | Wx3392vf_UCO_app.orders.office_id    | 1     | Using where                     |
| 1  |    SIMPLE   | client_users | eq_ref | PRIMARY        | PRIMARY   | 4       | Wx3392vf_UCO_app.orders.user_id      | 1     | Using index                     |
+----+-------------+--------------+--------+----------------+-----------+---------+--------------------------------------+-------+---------------------------------+

Answer 1

尝试从此查询开始：

SELECT * FROM jobs ORDER BY jobs.order_id DESC LIMIT 50

然后通过添加更多联接来增加其复杂性：

SELECT * FROM jobs 
LEFT JOIN job_item ON jobs.id = job_item.job_id
ORDER BY jobs.order_id DESC LIMIT 50

等

在每个步骤进行分析，您将能够找到瓶颈。可能是，其中一个连接表中的某个TEXT字段会降低查询速度或其他原因。

MYSQL慢ORDER BY

1 个答案: