提高 SQL 查询性能 [英] Increase SQL Query Performance

问题描述

数据库:

select distinct DateAdd(Day, DateDiff(Day, 0, m.Receive_date), 0) as Date,
(select count(*) from Raw_Mats A where DateAdd(Day, DateDiff(Day, 0, A.Receive_date), 0)=DateAdd(Day, DateDiff(Day, 0, m.Receive_date), 0)) as Total,
(select count(*) from Raw_Mats B where DateAdd(Day, DateDiff(Day, 0, B.Receive_date), 0)=DateAdd(Day, DateDiff(Day, 0, m.Receive_date), 0) and B.status='Solved') as Delivered,
(select count(*) from Raw_Mats C where DateAdd(Day, DateDiff(Day, 0, C.Receive_date), 0)=DateAdd(Day, DateDiff(Day, 0, m.Receive_date), 0) and C.status='Pending') as UnDelivered
from Raw_Mats m where m.Receive_date between '2011-07-01' and '2011-07-21'

如何提高上述查询的性能.它需要 44 秒.想让它少于 10 秒

How to increase the performance of the above query. It is taking 44 secs . wanna make it less than 10 secs

谢谢

推荐答案

Receive_date 和 status 是否都有索引?(不是每个的索引，组合)

Do you have an index on both Receive_date and status? (not an index on each, combined)

还有:

• 您在表中有 4 次接触，这意味着查询将至少扩展 O(4n).通过使用 COUNT(CASE) 您可以删除 Delivered 和 UnDelivered 子查询
• 也不需要简单的计数子查询
• 您需要 GROUP BY.您的 DISTINCT 可以解决这个问题
• BETWEEN 是 >= 和 <= 这对于带时间的日期来说通常是不正确的

• You have have 4 touches in the table which means the query will scale at least O(4n). By using COUNT(CASE) you can remove Delivered and UnDelivered subqueries
• The simple count subquery isn't needed either
• You need GROUP BY. YOur DISTINCT is a work around for that
• BETWEEN is >= and <= which isn't the usually correct for dates with times

为了清楚起见，我在这里使用了一个子查询，但这并不重要:

I've used a subquery here for clarity but it doesn't matter:

select
   DateOnly as Date,
   COUNT(*) AS Total,
   COUNT(CASE WHEN status='Solved' THEN 1 END) AS Delivered,
   COUNT(CASE WHEN status='Pending' THEN 1 END) AS UnDelivered
from
   (
   SELECT
       DateAdd(Day, DateDiff(Day, 0, m.Receive_date), 0) as DateOnly,
       status
   FROM
      Raw_Mats
   WHERE
      Receive_date >= '2011-07-01' AND Receive_date < '2011-07-21'
   ) T
 GROUP BY
   DateOnly

编辑，没有子查询.

我从一个子查询开始，因为我认为它比预期的更复杂并且没有费心把它拿出来......

I started with a subquery because I thought it's be more complex than expected and didn't bother taking it out...

select
   DateAdd(Day, DateDiff(Day, 0, m.Receive_date), 0) as Date,
   COUNT(*) AS Total,
   COUNT(CASE WHEN status='Solved' THEN 1 END) AS Delivered,
   COUNT(CASE WHEN status='Pending' THEN 1 END) AS UnDelivered
from
   Raw_Mats
WHERE
   Receive_date >= '2011-07-01' AND Receive_date < '2011-07-21'
GROUP BY
   DateAdd(Day, DateDiff(Day, 0, m.Receive_date), 0)

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