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我有一个半复杂的JOIN结构，可以根据订单从我的 MySQL 数据库中获取特定信息。首先让我给你 SQL Query；

SELECT
    #orders.*,
    orders.id,
    customers.lastname,
    customers.priority,
    shipments.status,
    pmv_sl.productmodelvariant_id,
    pmv_sl.nr AS pmv_nr,
    COALESCE(SUM(orderlines.nr), 0) AS orderlines_nr_count,
    COALESCE(SUM(shipment_lines.nr), 0) AS shipment_lines_nr_count
FROM orders
    INNER JOIN  customers       ON customers.id = orders.customer_id
    INNER JOIN  platforms       ON platforms.id = orders.platform_id
    INNER JOIN  stocklocations  ON stocklocations.id = platforms.stocklocation_id
    LEFT JOIN   orderlines      ON orderlines.order_id = orders.id
    LEFT JOIN   shipments       ON shipments.order_id = orders.id
    LEFT JOIN   shipment_lines  ON shipment_lines.shipment_id = shipments.id

    # This JOIN, together with shipment_lines, makes the query suddenly very slow (probably because of all the SUM()'s)
    LEFT JOIN   productmodelvariants_stocklocations pmv_sl ON
        pmv_sl.productmodelvariant_id = orderlines.productmodelvariant_id
        AND pmv_sl.stocklocation_id = stocklocations.id
WHERE
    orders.orderstatus_id = 2
    AND orders.order_all_to_shipment = 0
GROUP BY
    orders.id

问题

所以我计算了这个查询的 4 种速度（所有情况下都有 450 个结果）；

  1. 没有LEFT JOIN shipment_lines和没有LEFT JOIN productmodelvariants_stocklocations
  2. LEFT JOIN shipment_lines只有_
  3. LEFT JOIN productmodelvariants_stocklocations只有_
  4. 两者2.兼有3.

这是结果速度；

  1. 0.146 秒
  2. 1.975 秒
  3. 0.234 秒
  4. 4.619 秒

表格中的行

  • 行orderlines数：24528
  • 行shipment_lines数：6345
  • 行数productmodelvariants_stocklocations：1819

结论

如您所见，一次2.和3.(in 4.) 都参加了比赛；SQL 开始大汗淋漓。

我想知道是否有比我拥有更多（My）SQL 知识的人知道改变查询上下文以提高它的方法。

我还注意到，在执行4.和引用COALESCE(SUM()'s 时，我很容易获得0.8秒数1.0。

更新

解释扩展

解释扩展

4

2 回答 2

2

您正在通过未能在 shipping.status 上指定连接子句来创建交叉连接

尝试像这样重新组织您的查询：

SELECT A.*, 
    orders_id,
    customers.lastname,
    customers.priority,
#    shipments.status,
    pmv_sl.productmodelvariant_id,
    pmv_sl.nr AS pmv_nr,
    orderlines_nr_count,
    shipment_lines_nr_count
FROM (
  SELECT
      #orders.*,
      orders.id AS orders_id,
#      shipments.status,
      COALESCE(SUM(orderlines.nr), 0) AS orderlines_nr_count,
      COALESCE(SUM(shipment_lines.nr), 0) AS shipment_lines_nr_count
  FROM orders
      LEFT JOIN   orderlines      ON orderlines.order_id = orders.id
      LEFT JOIN   shipments       ON shipments.order_id = orders.id
      LEFT JOIN   shipment_lines  ON shipment_lines.shipment_id = shipments.id

  WHERE orders.orderstatus_id = 2
   AND orders.order_all_to_shipment = 0
  GROUP BY 
      orders.id,
      orderlines.productmodelvariant_id,
      stocklocations.id
) orders
    INNER JOIN  customers       ON customers.id = orders.customer_id
    INNER JOIN  platforms       ON platforms.id = orders.platform_id
    INNER JOIN  stocklocations  ON stocklocations.id = platforms.stocklocation_id
    LEFT JOIN   productmodelvariants_stocklocations pmv_sl ON
      pmv_sl.productmodelvariant_id = orderlines.productmodelvariant_id
      AND pmv_sl.stocklocation_id = stocklocations.id
GROUP BY
    orders.id

然后找出装运状态的去向。

于 2013-04-28T18:31:09.103 回答
1

对于任何给定的订单，您的查询正在订单和发货之间进行笛卡尔连接。更好的方法是在进行连接之前将所有内容汇总到该order_id级别：

SELECT
    #orders.*,
    orders.id,
    customers.lastname,
    customers.priority,
    shipments.status,
    pmv_sl.productmodelvariant_id,
    pmv_sl.nr AS pmv_nr,
    COALESCE(ol.orderlines_nr_count, 0) AS orderlines_nr_count,
    COALESCE(sl.shipment_lines_nr_count, 0) AS shipment_lines_nr_count
FROM orders
    INNER JOIN  customers       ON customers.id = orders.customer_id
    INNER JOIN  platforms       ON platforms.id = orders.platform_id
    INNER JOIN  stocklocations  ON stocklocations.id = platforms.stocklocation_id
    LEFT JOIN  
    (select order_id, SUM(orderlines.nr) as orderline_nr_count
     from orderlines
     group by order_id
    ) ol ON ol.order_id = orders.id
    LEFT JOIN   shipments       ON shipments.order_id = orders.id
    LEFT JOIN
    (select order_id, SUM(shipment_lines.nr) shipment_lines_nr_count
     from shipment_lines 
     group by order_id
    ) sl ON sl.shipment_id = shipments.id

    # This JOIN, together with shipment_lines, makes the query suddenly very slow (probably because of all the SUM()'s)
    LEFT JOIN   productmodelvariants_stocklocations pmv_sl ON
        pmv_sl.productmodelvariant_id = orderlines.productmodelvariant_id
        AND pmv_sl.stocklocation_id = stocklocations.id
WHERE
    orders.orderstatus_id = 2
    AND orders.order_all_to_shipment = 0
GROUP BY
    orders.id

这是一个近似值，因为我看到的唯一聚合函数是针对订单行和装运行。例如，如果每个订单有多个发货，您将必须弄清楚如何将其压缩为一种状态（您的原始查询将任意选择一种状态，就像这个查询一样）。

group by如果您只在该级别将表/子查询连接在一起，则不需要最后的order_id。

于 2013-04-28T19:16:25.410 回答