MySQL查询优化100000条带有左外连接的记录

Question

i have a clients table, and 100,000 records in it.

And also clients has alot of related tables, where stores a related data.

My query is like this:

SELECT COUNT(DISTINCT `clients2`.`id`) 
  FROM `clients2` as `clients2` 
  LEFT OUTER JOIN `users` as `users` 
    ON (    `clients2`.`user_id`=`users`.`id` 
         and users.status!=5 
         and clients2.status!=5
       ) 
LEFT OUTER JOIN `private_data` as `privateData` 
  ON (    `users`.`person_id`=`privateData`.`id` 
      and clients2.status!=5
     )

This is only 2 joins, but my real query has 5-7 joins. And it's very slow with 100,000 records. About 0.5 sec.

My database is very normalized. And it seems like i need to denormalize it now. Or maybe anyone can recommend a good solution ?

Answer 1

I think you could probably use some of the inbuilt optimization techniques of Mysql in itself for joins.

LEFT JOIN and RIGHT JOIN Optimization

Answer 2

如果数据库已规范化，则可以在查询中使用“常规”联接。这将大大加快速度。