如何加快多个内连接的SQL查询？

Question

我在下面的查询有效，但返回结果需要永远，我不知道如何优化它以显着减少时间。如果有人有任何建议，请告诉我。

提前致谢。

SELECT DISTINCT 
                u.ID,
                u.user_email,
                u.display_name,
                m.user_id,
                m1.meta_value AS first_name,
                m2.meta_value AS last_name,
                m3.meta_value AS descriptions,
                m4.meta_value AS company_name,
                m5.meta_value AS company_website,
                m6.meta_value AS phone,
                m7.meta_value AS company_address,
                m8.meta_value AS scategory,
                m9.meta_value AS facebook,
                m10.meta_value AS twitter,
                m11.meta_value AS linkedin,
                m12.meta_value AS youtube,
                m13.meta_value AS instagram,
                m14.meta_value AS googleplus,
                m15.meta_value AS specialties,
                m16.meta_value AS company_logo
           FROM $wpdb->users u 
           INNER JOIN $wpdb->usermeta m ON (m.user_id = u.ID)
           INNER JOIN $wpdb->usermeta m1 ON (m1.user_id = u.ID AND m1.meta_key = 'first_name')
           INNER JOIN $wpdb->usermeta m2 ON (m2.user_id = u.ID AND m2.meta_key = 'last_name')
           INNER JOIN $wpdb->usermeta m3 ON (m3.user_id = u.ID AND m3.meta_key = 'description')
           INNER JOIN $wpdb->usermeta m4 ON (m4.user_id = u.ID AND m4.meta_key = 'company_name')
           INNER JOIN $wpdb->usermeta m5 ON (m5.user_id = u.ID AND m5.meta_key = 'company_website')
           INNER JOIN $wpdb->usermeta m6 ON (m6.user_id = u.ID AND m6.meta_key = 'phone')
           INNER JOIN $wpdb->usermeta m7 ON (m7.user_id = u.ID AND m7.meta_key = 'company_address')
           INNER JOIN $wpdb->usermeta m8 ON (m8.user_id = u.ID AND m8.meta_key = 'scategory')
           INNER JOIN $wpdb->usermeta m9 ON (m9.user_id = u.ID AND m9.meta_key = 'facebook')
           INNER JOIN $wpdb->usermeta m10 ON (m10.user_id = u.ID AND m10.meta_key = 'twitter')
           INNER JOIN $wpdb->usermeta m11 ON (m11.user_id = u.ID AND m11.meta_key = 'linkedin')
           INNER JOIN $wpdb->usermeta m12 ON (m12.user_id = u.ID AND m12.meta_key = 'youtube')
           INNER JOIN $wpdb->usermeta m13 ON (m13.user_id = u.ID AND m13.meta_key = 'instagram')
           INNER JOIN $wpdb->usermeta m14 ON (m14.user_id = u.ID AND m14.meta_key = 'googleplus')
           INNER JOIN $wpdb->usermeta m15 ON (m15.user_id = u.ID AND m15.meta_key = 'specialties')
           INNER JOIN $wpdb->usermeta m16 ON (m16.user_id = u.ID AND m16.meta_key = 'company_logo')
           WHERE m.meta_key = 'wp_capabilities' 
           AND m.meta_value LIKE '%employer%' 
           ORDER BY u.ID

Answer 1

我真的没有看到你的自定义查询的重点。假设你有employer（或任何你命名的）的角色，更好的方法是做类似的事情

get_users( array( 'role' => 'employer' ) );

哪个应该返回具有employer角色的所有用户。然后你可以使用php进一步过滤它，这将快1000倍。

更不用说wp_capabilities不是一成不变的事实，而你用wp_替换$wpdb->prefix部分实际上更安全。

一旦知道用户ID，查询元数据总是比直接查询元数据更快。

Answer 2

在查看查询后，我意识到问题并不像我评论时那么简单，我不会删除它，但这是错误的。

我无法保证我构建的查询会更好，试一试并将其与当前的EXPLAIN进行比较：

SELECT DISTINCT 
      u.ID,
      u.user_email,
      u.display_name,
      m.user_id,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'first_name' AS first_name,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'last_name' AS last_name,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'descriptions' AS descriptions,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'company_name' AS company_name,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'company_website' AS company_website,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'phone' AS phone,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'company_address' AS company_address,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'scategory' AS scategory,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'facebook' AS facebook,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'twitter' AS twitter,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'linkedin' AS linkedin,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'youtube' AS youtube,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'instagram' AS instagram,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'googleplus' AS googleplus,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'specialties' AS specialties,
      SELECT t.meta_value FROM m WHERE m.meta_key = 'company_logo' AS company_logo
 FROM $wpdb->users u 
 INNER JOIN $wpdb->usermeta m ON (m.user_id = u.ID)
 WHERE m.meta_key = 'wp_capabilities' 
 AND m.meta_value LIKE '%employer%' 
 ORDER BY u.ID

这是使用子查询而不是多个JOIN语句的相同查询。我建议你做一些像这样的查询：

WITH cte(u_id, email, display_name, m_user_id)
 AS
 (
   SELECT 
       u.ID,
       u.user_email,
       u.display_name,
       m.user_id
   FROM $wpdb->users u 
   INNER JOIN $wpdb->usermeta m ON (m.user_id = u.ID)
   WHERE m.meta_key = 'wp_capabilities' 
   AND m.meta_value LIKE '%employer%' 
 )
 SELECT 
    u.u_id,
    u.email,
    u.display_name,
    u.m_user_id,
    m.meta_key,
    m.meta_value
FROM cte u
INNER JOIN $wpdb->usermeta m ON (m.user_id = u.u_id)
WHERE m.meta_key IN ('first_name'
                      'last_name'
                      'descriptions'
                      'company_name'
                      'company_website'
                      'phone'
                      'company_address'
                      'scategory'
                      'facebook'
                      'twitter'
                      'linkedin'
                      'youtube'
                      'instagram'
                      'googleplus'
                      'specialties'
                      'company_logo')
ORDER BY u.u_id

第二个查询将带来您需要的所有数据，您只需要在代码中执行某些操作即可获取与用户ID相关的所有字段并将它们放在同一对象中。