mysql - 如何优化此查询？

Question

SELECT DISTINCT wposts.* 
    FROM wp_2_posts wposts, wp_2_postmeta wpostmeta, wp_2_postmeta wpostmeta1, wp_2_term_taxonomy, wp_2_terms, wp_2_term_relationships
    WHERE wposts.ID = wpostmeta.post_id
    AND wp_2_terms.term_id = '8'
    AND wp_2_term_taxonomy.term_id = wp_2_terms.term_id
    AND wp_2_term_taxonomy.term_taxonomy_id = wp_2_term_relationships.term_taxonomy_id
    AND wp_2_term_relationships.object_id = wposts.ID
    AND wpostmeta.meta_key = 'validity'
    AND wpostmeta.meta_value > '".$logic_date."'    
AND wpostmeta1.meta_key != 'permanent'  
    AND wposts.post_status = 'publish' 
    AND wposts.post_type = 'post'
    ORDER BY wposts.post_date DESC

到目前为止的好建议，这里是仍然不使用第二个 meta_key 的 'evolved' 查询!= 'permanent_listing'

选择 wposts.* FROM wp_2_posts wposts LEFT JOIN wp_2_postmeta wpostmeta ON wposts.ID = wpostmeta.post_id LEFT JOIN wp_2_term_relationships wrelationships ON wrelationships.object_id = wposts.ID LEFT JOIN wp_2_term_taxonomy wtaxonomy ON wtaxonomy.term_taxonomy_id = wrelationships.term_taxonomy_id LEFT JOIN wp_2_terms wterms ON wtaxonomy.term_id = wterms.term_id 在哪里 wterms.term_id = '--此处的类别 ID--' 和 wpostmeta.meta_key = 'wpx_validity' 和 wpostmeta.meta_value > '--今天的日期在这里--' AND wpostmeta.meta_key != 'permanent_listing' 和 wposts.post_status = '发布' 和 wposts.post_type = 'post' 按 wposts.post_date DESC 排序

LEFT JOIN 和 INNER JOIN 似乎做同样的事情。 存在以下索引:wp_2_terms.term_id、wp_term_taxonomy.term_taxonomy_id、wp_2_term_relationships.object_id wp_2_postmeta 有一个 meta_id 索引和字段:post_id、meta_key、meta_value。

此查询正在 WPMU 上运行。

Answer 1

首先我建议您使用 INNER JOIN 语法来连接表:

SELECT table1.c1, table2.c2 FROM table1
  INNER JOIN table2 ON table1.ck = table2.ck

您还应该避免使用 * 运算符并仔细选择您需要的列。 DISTINCT 还会减慢您的查询速度。你真的需要它吗？