Mysql 左连接速度很慢

Question

我有一个左连接:

$query = "SELECT a.`id`, a.`documenttitle`, a.`committee`, a.`issuedate`, b.`tagname`
   FROM `#__document_management_documents` AS a 
   LEFT JOIN `#__document_managment_tags` AS b 
   ON a.id = b.documentid 
   ".$tagexplode."
   ".$issueDateText."
   AND a.committee in (".$committeeQueryTextExplode.")
   AND a.documenttitle LIKE '".$documentNameFilter."%'
   GROUP BY a.id ORDER BY a.documenttitle ASC

  ";

4000条记录时确实很慢，大约7秒

任何想法我可能做错了什么

SELECT a.`id`, a.`documenttitle`, a.`committee`, a.`issuedate`, b.`tagname` 
FROM `w4c_document_management_documents` AS a 
LEFT JOIN `document_managment_tags` AS b 
ON a.id = b.documentid WHERE a.issuedate >= '' 
AND a.committee in ('1','8','9','10','11','12','13','16','17','18','19','20','21','22','23','24','25','26','27','28','29','30','31','32','33','34','35','36','37','38','39','40','41','42','43','44','45','46','47') 
AND a.documenttitle LIKE '%' GROUP BY a.id ORDER BY a.documenttitle ASC

Answer 1

我会在 a.committee 上建立一个索引，并在文档标题栏上建立全文索引。 IN 和 LIKE 对我来说是直接的标志。发布日期也应该有一个索引，因为您 >= 它