mysql解释结果解释

Question

下面的查询完全符合我的预期，是直观的，不会生成中间表。缺点是需要很长时间才能完成。

在这种情况下我要做的是逐步打破查询并创建那些中间表＆amp;索引。这一次，我想更好地处理解释提供的提示，并希望得到任何指示：我在下面的查询中遗漏了哪些明显的优化步骤？

根据MySQL query optimization and EXPLAIN for a noob中的建议，我在order_number的{​​{1}}，order_type和item创建了索引。然而，目前还不清楚这些将如何带来字符处理/正则表达式。

orders_raw

编辑，@ ing tran：我还没有严格计算上面的查询和你的查询（经过几次修改，下面复制后），从空闲机器开始。我确实提交了它，并没有看到运行时间明显减少。

SELECT bundle_headers.order_number , bundle_headers.title , digital_subs.subscription_id , 1 as bundle_component
from
(
  select order_number , substring( item , 1 , 3 ) as title , quantity from orders_raw
  where order_type in (4,6)                      
) bundle_headers
inner join
(
  select order_number , subscription_id , item as title , quantity from orders_raw
  where order_type = 0 and length( item ) = 4    
) digital_subs
on bundle_headers.order_number = digital_subs.order_number and
   digital_subs.title regexp concat( '.*' , bundle_headers.title , '.*' ) and
   bundle_headers.quantity = digital_subs.quantity

UNION


SELECT bundle_headers.order_number , bundle_headers.title , print_subs.subscription_id , 1 as bundle_component
from
(
  select order_number , substring( item , 1 , 3 ) as title , quantity from orders_raw
  where order_type in (4,6)                      
) bundle_headers
inner join
(
  select order_number , subscription_id , item as title , quantity from orders_raw
  where order_type = 0 and length( item ) = 3    
) print_subs
on bundle_headers.order_number = print_subs.order_number and
   print_subs.title regexp concat( '.*' , bundle_headers.title , '.*' ) and
   bundle_headers.quantity = print_subs.quantity;

Answer 1

请尝试此查询，看看它是否产生相同的结果。如果它更快

SELECT bundle_headers.order_number,substring(bundle_headers.title,1,3) as title,subs.subscription_id,1 as bundle_component
FROM order_type bundle_headers
INNER JOIN orders_raw subs ON (bundle_headers.order_number = subs.order_number)
WHERE (bundle_headers.order_type = 4 OR bundle_headers.order_type = 6)
  AND subs.order_type = 0
  AND bundle_headers.quantity = subs.quantity
  AND subs.title LIKE CONCAT('%',substring(bundle_headers.title,1,3),'%')
  AND (length(subs.item) = 4 OR length(subs.item) = 3)