2個表上的INNER JOIN返回錯誤的值

Question

這是我的SQL查詢：

SELECT  SUM(amz_event_shipment_items.quantity),
        amz_event_shipment_items.seller_sku

FROM    amz_event_shipment_items

INNER   JOIN amz_event_fees         ON amz_event_shipment_items.id = amz_event_fees.shipment_item_id
INNER   JOIN amz_shipment_events    ON amz_shipment_events.id = amz_event_shipment_items.shipment_event_id

WHERE   amz_event_fees.currency  = 'USD'
        AND amz_shipment_events.event_type <> 'RefundEvent'
        AND amz_shipment_events.posted_date BETWEEN '2016-5-1 07:00:00' AND '2016-5-7 06:59:59'

GROUP   BY amz_event_shipment_items.seller_sku

但是返回的值太高了。。。對我來說沒有意義。

我有什么想念的嗎？

編輯

Many shipment_events for each date

Each shipment_event HAS MANY shipment_item / BELONGS TO ONE event

Each shipment_item HAS MANY shipment_fee  / BELONGS TO ONE item

Answer 1

您將數量乘以費用數量。 尋找純粹的存在時，請使用IN或EXISTS子句。

select 
  sum(i.quantity), 
  i.seller_sku
from amz_event_shipment_items i
where exists
(
  select *
  from amz_event_fees f
  where f.currency  = 'USD'
  and f.shipment_item_id = i.id
)
and exists
(
  select *
  from amz_shipment_events e
  where e.event_type <> 'RefundEvent'
  and e.posted_date between '2016-05-01 07:00:00' and '2016-05-07 06:59:59'
  and e.id = i.shipment_event_id
)
group by i.seller_sku;

（MySQL有時在IN子句上運行緩慢，因此盡管我更喜歡IN ，但我在這里使用EXISTS 。）

Answer 2

這不是答案，而是附件。 如果我理解正確，則您的查詢返回了錯誤的結果，但速度相當快，而我的（帶有EXISTS子句）返回了正確的結果，但速度非常慢。

因此，消除重復項的任務似乎花費了太多時間。

這里有兩個想法：

第一個想法：立即消除重復

除了加入費用之外，我們在加入之前先匯總費用：

select 
  sum(i.quantity), 
  i.seller_sku
from amz_event_shipment_items i
join -- join with only one record per ID to substitute an EXISTS clause
(
  select distinct shipment_item_id
  from amz_event_fees
  where f.currency  = 'USD'
) f on f.shipment_item_id = i.id
and exists
(
  select *
  from amz_shipment_events e
  where e.event_type <> 'RefundEvent'
  and e.posted_date between '2016-05-01 07:00:00' and '2016-05-07 06:59:59'
  and e.id = i.shipment_event_id
)
group by i.seller_sku;

第二個想法：預先匯總值

在這里，我們嘗試盡快進行匯總，以使中間結果保持較小，而不必為每個項目記錄查找事件表。

select 
  sum(i.pre_sum_quantity), 
  i.seller_sku
from 
(
  select seller_sku, shipment_event_id, sum(quantity) as pre_sum_quantity
  from amz_event_shipment_items
  where exists
  (
    select *
    from amz_event_fees f
    where f.currency  = 'USD'
    and f.shipment_item_id = amz_event_shipment_items.id
  )
  group by seller_sku, shipment_event_id
) i
where exists
(
  select *
  from amz_shipment_events e
  where e.event_type <> 'RefundEvent'
  and e.posted_date between '2016-05-01 07:00:00' and '2016-05-07 06:59:59'
  and e.id = i.shipment_event_id
)
group by i.seller_sku;

如果事件類型很少，您也可以嘗試擺脫<> ，從而使它更有可能使用索引：

where e.event_type in ('EarlyPaymentEvent','LatePaymentEvent')

（在這種情況下，它可能會支付有哪里指數event_type而來的前posted_date 。）

我必須承認，我認為這不會比原始的EXISTS查詢快得多，但是值得一試。

Answer 3

您的聯接之一返回的記錄可能比您預期的要多。 我會嘗試做一個select *然后按sku和目測結果排序。