我们如何加快查询速度*

Question

我已经编写了这段代码来查询mysql表的customerselections，companies和companycampaigns。表格包含必要字段的索引。

查询时间（没有缓存）大约是0,30。考虑并发连接，我认为查询时间很长。是否可以以不同的方式重写以加快查询时间？

SELECT  
customerselections.customer_id, 
customerselections.selectedcompany_id,
customerselections.selection_id,

companycampaigns.campaign_id,
companycampaigns.company_id,
companycampaigns.campaign_title,
companycampaigns.campaign_detail,
companycampaigns.published,

companies.company_logo,
companies.company_id,


FROM  customerselections
LEFT JOIN companies ON customerselections.selectedcompany_id=companies.company_id 
LEFT  JOIN companycampaigns ON  companycampaigns.company_id=companies.company_id AND companycampaigns.published='1'
WHERE customerselections.customer_id='$customerid'  LIMIT $offset,$limit 

Answer 1

基于像customerselections.customer_id这样的字段进行选择比选择所有行要慢，因为服务器不需要进行任何过滤。所以这会给予一点点提升。

SELECT  
customerselections.*,
companycampaigns.*,
companies.*
FROM  customerselections
LEFT JOIN companies ON customerselections.selectedcompany_id=companies.company_id 
LEFT  JOIN companycampaigns ON  companycampaigns.company_id=companies.company_id AND companycampaigns.published='1'
WHERE customerselections.customer_id='$customerid'  LIMIT $offset,$limit 

Answer 2

尝试在companycampaigns (company_id, published)上定义综合索引并查看EXPLAIN计划，看看它是否有帮助。