MySQL 连接优化：使用派生表和 GROUP BY 改进连接类型

Question

我正在尝试改进执行以下操作的查询：

对于每项工作，将所有成本相加，将发票金额相加，然后计算损益。成本来自几个不同的表，例如采购订单、用户事件（工程师分配的时间/他在现场花费的时间）、使用的库存等。
该查询还需要输出一些其他列，例如作品的站点名称，以便该列可以排序（在所有这些之后附加一个 ORDER BY）。

SELECT
    jobs.job_id,
    jobs.start_date,
    jobs.end_date,
    events.time,
    sites.name site,
    IFNULL(stock_cost,0) stock_cost,
    labour,
    materials,
    labour+materials+plant+expenses revenue,
    (labour+materials+plant)-(time*3557/360000+IFNULL(orders_cost,0)+IFNULL(stock_cost,0)) profit,
    ((labour+materials+plant)-(time*3557/360000+IFNULL(orders_cost,0)+IFNULL(stock_cost,0)))/(time*3557/360000+IFNULL(orders_cost,0)+IFNULL(stock_cost,0)) ratio

FROM
    jobs

    LEFT JOIN (
        SELECT
            job_id,
            SUM(labour_charge) labour,
            SUM(materials_charge) materials,
            SUM(plant_hire_charge) plant,
            SUM(expenses) expenses
        FROM invoices
        GROUP BY job_id
        ORDER BY NULL
    ) invoices USING(job_id)

    LEFT JOIN (
        SELECT
            job_id,
            SUM(IF(start_onsite && end_onsite,end_onsite-start_onsite,end-start)) time,
            SUM(travel+parking+materials) user_expenses
        FROM users_events
        WHERE type='job'
        GROUP BY job_id
        ORDER BY NULL
    ) events USING(job_id)

    LEFT JOIN (
        SELECT
            job_id,
            SUM(IFNULL(total,0))*0.01 orders_cost
        FROM purchaseorders
        GROUP BY job_id
        ORDER BY NULL
    ) purchaseorders USING(job_id)

    LEFT JOIN (
        SELECT
            location job_id,
            SUM(amount*cost))*0.01 stock_cost
        FROM stock_location
        LEFT JOIN stock_items ON stock_items.id=stock_location.stock_id
        WHERE location>=3000 AND amount>0 AND cost>0
        GROUP BY location
        ORDER BY NULL
    ) stock USING(job_id)

    LEFT JOIN contacts_sites sites ON sites.id=jobs.site_id;

我读到了这个：http://dev.mysql.com/doc/refman/5.0/en/group-by-optimization.html，但看不到我如何/是否可以在其中应用任何东西。 出于测试目的，我尝试在左侧、右侧和中心字段上添加各种索引，但对 EXPLAIN 输出没有任何改进：

+----+-------------+----------------+--------+------------------------+---------+---------+------------------------------------+-------+-------------------------------+
| id | select_type | table          | type   | possible_keys          | key     | key_len | ref                                | rows  | Extra                         |
+----+-------------+----------------+--------+------------------------+---------+---------+------------------------------------+-------+-------------------------------+
|  1 | PRIMARY     | jobs           | ALL    | NULL                   | NULL    | NULL    | NULL                               |  7088 |                               |
|  1 | PRIMARY     | <derived2>     | ALL    | NULL                   | NULL    | NULL    | NULL                               |  5038 |                               |
|  1 | PRIMARY     | <derived3>     | ALL    | NULL                   | NULL    | NULL    | NULL                               |  6476 |                               |
|  1 | PRIMARY     | <derived4>     | ALL    | NULL                   | NULL    | NULL    | NULL                               |   904 |                               |
|  1 | PRIMARY     | <derived5>     | ALL    | NULL                   | NULL    | NULL    | NULL                               |   531 |                               |
|  1 | PRIMARY     | sites          | eq_ref | PRIMARY                | PRIMARY | 4       | bestbee_db.jobs.site_id            |     1 |                               |
|  5 | DERIVED     | stock_location | ALL    | stock,location,amount,…| NULL    | NULL    | NULL                               |  5426 | Using where; Using temporary; |
|  5 | DERIVED     | stock_items    | eq_ref | PRIMARY                | PRIMARY | 4       | bestbee_db.stock_location.stock_id |     1 | Using where                   |
|  4 | DERIVED     | purchaseorders | ALL    | NULL                   | NULL    | NULL    | NULL                               |  1445 | Using temporary;              |
|  3 | DERIVED     | users_events   | ALL    | type,type_job          | NULL    | NULL    | NULL                               | 11295 | Using where; Using temporary; |
|  2 | DERIVED     | invoices       | ALL    | NULL                   | NULL    | NULL    | NULL                               |  5320 | Using temporary;              |
+----+-------------+----------------+--------+------------------------+---------+---------+------------------------------------+-------+-------------------------------+

生成的行数为 5 x 10^21（低于我开始优化此查询之前的 3 x 10^42！）
目前执行需要 7 秒（从 26 秒减少），但我希望不到 1 秒。

顺便说一句：GROUP BY x ORDER BY NULL 是消除子查询中不必要的文件排序的好方法！ （来自http://www.mysqlperformanceblog.com/2006/09/04/group_concat-useful-group-by-extension/）

Answer 1

根据您对我的问题的评论，我将执行以下操作...

在最顶端...

SELECT STRAIGHT_JOIN（只需添加“STRAIGH_JOIN”关键字）

然后，对于发票、事件、p/o 等的每个子查询，将 ORDER BY 显式更改为 JOB_ID，这样它可能有助于针对主 JOBS 表连接进行优化。

最后，确保您的每个子查询表在 Job_ID（Invoices、User_events、PurchaseOrders、Stock_Location）上都有一个索引

此外，对于 Stock_Location 表，您可能希望通过在上添加复合索引来帮助子查询的 WHERE 子句
(job_id, location, amount) 三个字段深度应该足够了，即使你有键加上 3 个 where 条件元素。