MySQL查询缓存，复杂SQL查询

下面的问题让我头疼

我已经将MySQL服务器设置为使用查询查询查询

set global query_cache_size = 10000000;

我的查询缓存似乎可以工作，因为

SHOW STATUS LIKE 'Qcache%';  

详情如下:

+-------------------------+----------+    
|    Variable_name        | Value    |           
+-------------------------+----------+     
| Qcache_free_blocks      | 1        |
| Qcache_free_memory      | 47223976 |
| Qcache_hits             | 6709     |                                       
| Qcache_inserts          | 2314     |                                    
| Qcache_lowmem_prunes    | 0        |                                  
| Qcache_not_cached       | 365      |                                  
| Qcache_queries_in_cache | 441      |                                   
| Qcache_total_blocks     | 960      |                                     
+-------------------------+----------+ 

但是，以下带有内部选择等的复杂查询不会被缓存

检索此查询的数据通常至少需要0.8秒。我如何让mysql将查询结果存储在缓存中

我试着去除内部的选择，但这没有什么不同

SELECT p.id
   AS
   project_id,
   p.code
   AS project_code,
   p.title
   AS project_title,
   p.start_date
   AS project_start_date,
   p.end_date
   AS project_end_date,
   p.modf
   AS project_modf,
   ( p.budget * (SELECT 1 / r.VALUE
                 FROM   exchange_rates r
                 WHERE  r.class_currency_id = p.class_budget_currency_id) )
   AS
   project_budget,
   (SELECT z.txt
    FROM   sys_labels z
    WHERE  z.id = ps.value_label_id
           AND z.lng = 'en')
   AS project_status,
   (SELECT z.txt
    FROM   sys_labels z
    WHERE  z.id = ps.data_label_id
           AND z.lng = 'en')
   AS project_color,
   GROUP_CONCAT(DISTINCT pt.class_topic_id)
   AS projects_thematic_area_ids,
   u.id
   AS project_owner_id
FROM   projects AS p
   LEFT JOIN projects_thematic_areas AS pt
     ON pt.project_id = p.id
   LEFT JOIN sys_users AS u
     ON u.id = p.owner_uid
   LEFT JOIN class_data s
     ON s.id = p.class_status_id
   LEFT JOIN class_data AS ps
     ON ps.id = s.id
   LEFT JOIN sys_labels AS prdz1
     ON prdz1.id = prd.value_label_id
        AND prdz1.lng = 'en'
   LEFT JOIN sys_labels AS prdz2
     ON prdz2.id = prd.data_label_id
        AND prdz2.lng = 'en'
   LEFT JOIN projects_locations AS pl
     ON pl.project_id = p.id
   LEFT JOIN class_data AS l
     ON l.id = pl.class_location_id
   LEFT JOIN class_data AS r
     ON r._lft <= l._lft
        AND r._rgt >= l._rgt
        AND r._level = 1
        AND r.class_id = 5
   LEFT JOIN class_data AS c
     ON c._lft <= l._lft
        AND c._rgt >= l._rgt
        AND c._level = 2
        AND c.class_id = 10
   LEFT JOIN projects_donors AS pd
     ON pd.project_id = p.id
   LEFT JOIN institutions AS i
     ON pd.inst_id = i.id
   LEFT JOIN class_data AS ic
     ON ic.id = i.class_country_id
   LEFT JOIN projects_deliverables AS d
     ON d.project_id = p.id
WHERE  1 = 1
   AND p.is_del = "f"
   AND p.is_active = "t"
GROUP  BY p.id
ORDER  BY p.modf DESC,
      p.code DESC 

有什么帮助吗

问候

---

J.

您可以尝试选择SQL\u缓存。。。从…

除前面的答案外：如果所选表中有任何更改，则即使查询在其中，也不会使用查询缓存

但是，当你没有从这些表格中选择任何内容时，为什么要加入这些表格呢？此外，如果您可以加入，您可能不应该再选择任何内容

类似这样的内容将选择完全相同的：

SELECT
   p.id AS project_id,
   p.code AS project_code,
   p.title AS project_title,
   p.start_date AS project_start_date,
   p.end_date AS project_end_date,
   p.modf AS project_modf,
   p.budget * (1 / r.VALUE) AS project_budget,
   z1.txt AS project_status,
   z2.txt AS project_color,
   GROUP_CONCAT(DISTINCT pt.class_topic_id) AS projects_thematic_area_ids,
   u.id AS project_owner_id
FROM
   projects AS p
   LEFT JOIN projects_thematic_areas AS pt ON pt.project_id = p.id
   LEFT JOIN sys_users AS u ON u.id = p.owner_uid
   LEFT JOIN exchange_rates AS r ON r.class_currency_id = p.class_budget_currency_id
   LEFT JOIN class_data s ON s.id = p.class_status_id
   LEFT JOIN class_data AS ps ON ps.id = s.id
   LEFT JOIN sys_labels AS z1 ON z1.id = ps.value_label_id AND z1.lng = 'en'
   LEFT JOIN sys_labels AS z2 ON z2.id = ps.data_label_id AND z2.lng = 'en'
WHERE
   1
   AND p.is_del = "f"
   AND p.is_active = "t"
GROUP  BY
   p.id
ORDER  BY
   p.modf DESC,
   p.code DESC 

---

当然，您已经在所有外键上组合了索引，其中包括字段和组字段。考虑使用TyyIn或EnUM字段用于布尔值。您可能还想考虑不选择GROMPK-CONTAT，这样您就可以丢失该组。如果确定存在这种关系，也许可以使用内部联接而不是左联接。

您可以尝试一些基本的方法：

阅读以确保您了解基本知识并正确设置。 理想情况下，隔离MySQL数据库服务器，使其只运行您给它的命令。如果无法执行此操作，请尝试在另一台计算机上设置并运行测试。 运行一个简单的查询并查看Qcache_hits和Com_select状态变量，以确定查询缓存是否被命中。 尝试复杂的查询并监视相同的值。如果您的查询没有命中缓存，请尝试较小的部分，直到找到导致它无法缓存的原因。如果正在缓存，则问题可能是由于查询中的任何表在查询之间被更新，这将使缓存的副本无效。