Question

我使用以下查询：

SELECT *,  
GROUP_CONCAT(distinct t_name order by t_id separator ', ') 'Topics', 
GROUP_CONCAT(distinct ch_title order by ch_id separator ', ') 'Chapters', 
GROUP_CONCAT(distinct cs_code order by cs_id separator ', ') 'ContentStandards', 
GROUP_CONCAT(distinct c_name order by c_id separator ', ') 'Categories', 
GROUP_CONCAT(distinct s_name order by s_id separator ', ') 'SchoolSubjects' 
FROM (
SELECT r.res_id, r.res_status, r.res_type, r.res_category, r.res_title, r.res_filename, r.res_source, r.res_gradelevel_from, r.res_gradelevel_to, r.res_tags, r.res_description, r.res_onserver, r.res_favoriteaccts, r.res_CreatedOn, c_id, s_id, t_id, ch_id, cs_id, 
CONCAT("<a class=""ReportLink"" href=""page.asp?category=",c_name,""" title=""",c_name,""">",c_name,"</a>") as c_name, 
CONCAT("<a class=""ReportLink"" href=""page.asp?subject=",s_name,""" title=""",s_name,""">",s_name,"</a>") as s_name, 
CONCAT("<a class=""ReportLink"" href=""page.asp?topic=",t_name,""" title=""",t_name,""">",t_name,"</a>") as t_name, 
CONCAT("<a class=""ReportLink"" href=""page.asp?cs=",cs_code,""" title=""",cs_code,""">",cs_code,"</a>") as cs_code, 
CONCAT("<a class=""ReportLink"" href=""page.asp?chapter=",ch_title,""" title=""",ch_title,""">",ch_code,": ",ch_title,"</a>") as ch_title 
FROM hre_resources r 
LEFT JOIN topic_to_resource ttr ON ttr.rt_resourceid = r.res_id 
LEFT JOIN topics t on t.t_id = ttr.rt_topicid 
LEFT JOIN topic_to_cs tcs on tcs.cst_topicid = t.t_id 
LEFT JOIN categories c ON c_id = r.res_category 
LEFT JOIN topic_to_framework ttc on ttc.ft_topicid = t.t_id 
LEFT JOIN ca_hss_frameworkchapters ch ON ch.ch_id = ttc.ft_frameworkid 
LEFT JOIN ca_hss_contentstandards cs ON cs.cs_id = tcs.cst_contentstandardid 
LEFT JOIN schoolsubjects_to_resource str ON str.sr_resid = r.res_id 
LEFT JOIN schoolsubjects s ON s.s_id = str.sr_sid) links 
WHERE RES_Status = 'Active' 
GROUP BY RES_ID 
ORDER BY RES_Title ASC, RES_Source DESC

此查询从mySQL数据库返回64个格式正确的记录，但执行此操作需要100多秒。

查询分析器将关键违规者显示为：

+-------------------------------+-----------+
|         Sending data          | 34.530026 |
+-------------------------------+-----------+
| Creating sort index           | 24.205878 |
| Storing result in query cache | 56.739204 |
+-------------------------------+-----------+

EXPLAIN结果如下：

+----+-------------+------------+--------+---------------+---------------+---------+------------------------------------+------+---------------------------------------------------------------------+
| id | select_type |   table    |  type  | possible_keys |      key      | key_len |                ref                 | rows |                                Extra                                |
+----+-------------+------------+--------+---------------+---------------+---------+------------------------------------+------+---------------------------------------------------------------------+
|  1 | PRIMARY     | <derived2> | ref    | <auto_key0>   | <auto_key0>   | 77      | const                              |   10 | Using index condition; Using where; Using temporary; Using filesort |
|  2 | DERIVED     | r          | ALL    | NULL          | NULL          | NULL    | NULL                               |   64 | NULL                                                                |
|  2 | DERIVED     | ttr        | ref    | RT_ResourceID | RT_ResourceID | 4       | uhri_hre.r.RES_ID                  |    3 | Using where                                                         |
|  2 | DERIVED     | t          | eq_ref | PRIMARY       | PRIMARY       | 4       | uhri_hre.ttr.RT_TopicID            |    1 | Using where                                                         |
|  2 | DERIVED     | tcs        | ref    | CST_TopicID   | CST_TopicID   | 4       | uhri_hre.t.T_ID                    |    9 | Using where                                                         |
|  2 | DERIVED     | c          | eq_ref | PRIMARY       | PRIMARY       | 4       | uhri_hre.r.RES_Category            |    1 | Using where                                                         |
|  2 | DERIVED     | ttc        | ref    | FT_TopicID    | FT_TopicID    | 4       | uhri_hre.t.T_ID                    |   21 | Using where                                                         |
|  2 | DERIVED     | ch         | eq_ref | PRIMARY       | PRIMARY       | 4       | uhri_hre.ttc.FT_FrameworkID        |    1 | Using where                                                         |
|  2 | DERIVED     | cs         | eq_ref | PRIMARY       | PRIMARY       | 4       | uhri_hre.tcs.CST_ContentStandardID |    1 | Using where                                                         |
|  2 | DERIVED     | str        | ref    | SR_RESID      | SR_RESID      | 4       | uhri_hre.r.RES_ID                  |    1 | Using where                                                         |
|  2 | DERIVED     | s          | eq_ref | PRIMARY       | PRIMARY       | 4       | uhri_hre.str.SR_SID                |    1 | Using where                                                         |
+----+-------------+------------+--------+---------------+---------------+---------+------------------------------------+------+---------------------------------------------------------------------+

表格包含以下索引。未列出的表在ID字段（主键）上具有索引：

HRE_Resources:
+--------------+-------+--------+--------+--------------+-------------+-----------+------+---------+
|   Keyname    | Type  | Unique | Packed |    Column    | Cardinality | Collation | Null | Comment |
+--------------+-------+--------+--------+--------------+-------------+-----------+------+---------+
| PRIMARY      | BTREE | Yes    | No     | RES_ID       |          64 | A         |      |         |
| RES_Type     | BTREE | No     | No     | RES_Type     |           4 | A         |      |         |
| RES_Category | BTREE | No     | No     | RES_Category |          10 | A         |      |         |
| RES_Status   | BTREE | No     | No     | RES_Status   |           4 | A         |      |         |
| RES_Language | BTREE | No     | No     | RES_Language |           8 | A         |      |         |
| RES_Source   | BTREE | No     | No     | RES_Source   |          21 | A         |      |         |
+--------------+-------+--------+--------+--------------+-------------+-----------+------+---------+

Topics:
+---------+-------+--------+--------+--------+-------------+-----------+------+---------+
| Keyname | Type  | Unique | Packed | Column | Cardinality | Collation | Null | Comment |
+---------+-------+--------+--------+--------+-------------+-----------+------+---------+
| PRIMARY | BTREE | Yes    | No     | T_ID   |          39 | A         |      |         |
| T_Name  | BTREE | No     | No     | T_Name |          39 | A         |      |         |
+---------+-------+--------+--------+--------+-------------+-----------+------+---------+

Topic_to_CS:
+-----------------------+-------+--------+--------+-----------------------+-------------+-----------+------+---------+
|        Keyname        | Type  | Unique | Packed |        Column         | Cardinality | Collation | Null | Comment |
+-----------------------+-------+--------+--------+-----------------------+-------------+-----------+------+---------+
| PRIMARY               | BTREE | Yes    | No     | CST_ID                |         685 | A         |      |         |
| CST_ContentStandardID | BTREE | No     | No     | CST_ContentStandardID |         228 | A         |      |         |
| CST_TopicID           | BTREE | No     | No     | CST_TopicID           |          76 | A         |      |         |
+-----------------------+-------+--------+--------+-----------------------+-------------+-----------+------+---------+

Topic_to_Framework:
+----------------+-------+--------+--------+----------------+-------------+-----------+------+---------+
|    Keyname     | Type  | Unique | Packed |     Column     | Cardinality | Collation | Null | Comment |
+----------------+-------+--------+--------+----------------+-------------+-----------+------+---------+
| PRIMARY        | BTREE | Yes    | No     | FT_ID          |         471 | A         |      |         |
| FT_TopicID     | BTREE | No     | No     | FT_TopicID     |          22 | A         |      |         |
| FT_FrameworkID | BTREE | No     | No     | FT_FrameworkID |         235 | A         |      |         |
+----------------+-------+--------+--------+----------------+-------------+-----------+------+---------+

Topic_to_Resource:
+---------------+-------+--------+--------+---------------+-------------+-----------+------+---------+
|    Keyname    | Type  | Unique | Packed |    Column     | Cardinality | Collation | Null | Comment |
+---------------+-------+--------+--------+---------------+-------------+-----------+------+---------+
| PRIMARY       | BTREE | Yes    | No     | RT_ID         |         387 | A         |      |         |
| RT_ResourceID | BTREE | No     | No     | RT_ResourceID |         129 | A         |      |         |
| RT_TopicID    | BTREE | No     | No     | RT_TopicID    |          77 | A         |      |         |
+---------------+-------+--------+--------+---------------+-------------+-----------+------+---------+

Schoolsubject_to_Resource:
+----------+-------+--------+--------+----------+-------------+-----------+------+---------+
| Keyname  | Type  | Unique | Packed |  Column  | Cardinality | Collation | Null | Comment |
+----------+-------+--------+--------+----------+-------------+-----------+------+---------+
| PRIMARY  | BTREE | Yes    | No     | SR_ID    |         228 | A         |      |         |
| SR_SID   | BTREE | No     | No     | SR_SID   |          25 | A         |      |         |
| SR_RESID | BTREE | No     | No     | SR_RESID |         228 | A         |      |         |
+----------+-------+--------+--------+----------+-------------+-----------+------+---------+

Categories:
+---------+-------+--------+--------+--------+-------------+-----------+------+---------+
| Keyname | Type  | Unique | Packed | Column | Cardinality | Collation | Null | Comment |
+---------+-------+--------+--------+--------+-------------+-----------+------+---------+
| PRIMARY | BTREE | Yes    | No     | C_ID   |           9 | A         |      |         |
| C_Name  | BTREE | No     | No     | C_Name |           9 | A         |      |         |
+---------+-------+--------+--------+--------+-------------+-----------+------+---------+

其中一些索引是使用在其他查询中使用的更复杂的WHERE创建的。

我在数据库上运行复杂的查询，用于与上述查询无关的其他目的，并且名义上执行。因此，我不认为这是服务器资源问题。

任何人都可以在上面的查询中看到可能导致如此缓慢响应的任何内容吗？

非常感谢提前！

PS。根据以下请求从服务器添加一些信息...

+------------------------------+---------+
|        Variable_name         |  Value  |
+------------------------------+---------+
| query_alloc_block_size       | 8192    |
| query_cache_limit            | 1048576 |
| query_cache_min_res_unit     | 4096    |
| query_cache_size             | 1048576 |
| query_cache_type             | ON      |
| query_cache_wlock_invalidate | OFF     |
| query_prealloc_size          | 8192    |
+------------------------------+---------+

+-------------------------+--------+
|      Variable_name      | Value  |
+-------------------------+--------+
| Qcache_free_blocks      |      9 |
| Qcache_free_memory      |  22736 |
| Qcache_hits             | 121910 |
| Qcache_inserts          |   9296 |
| Qcache_lowmem_prunes    |   8213 |
| Qcache_not_cached       |  29475 |
| Qcache_queries_in_cache |    103 |
| Qcache_total_blocks     |    295 |
+-------------------------+--------+

Answer 1

正如我在上面的评论中提到的，您似乎从多个表关系中获取了大量数据。这导致了几个Cartesian products，这就是你获得626K行的原因。

解决方案是将其分解为单个查询。

以下是我对您的模型的理解：

以下是各个查询的内容，以及各自的EXPLAIN计划。

您可以看到这消除了所有子查询和临时表，它消除了笛卡尔积，因此您不需要在任何地方使用DISTINCT，并且所有连接都很好地对抗主键。它可能看似重复，但查询更优化的事实应该使它运行得更快。

EXPLAIN
SELECT r.res_id, r.res_status, r.res_type, r.res_category, r.res_title, r.res_filename,
  r.res_source, r.res_gradelevel_from, r.res_gradelevel_to, r.res_tags, r.res_description,
  r.res_onserver, r.res_favoriteaccts, r.res_CreatedOn, c.c_name AS 'Categories'
FROM hre_resources AS r
INNER JOIN categories c ON c_id = r.res_category 
WHERE r.res_status = 'Active'
--------------

+----+-------------+-------+--------+-------------------------+------------+---------+---------------------+------+-----------------------+
| id | select_type | table | type   | possible_keys           | key        | key_len | ref                 | rows | Extra                 |
+----+-------------+-------+--------+-------------------------+------------+---------+---------------------+------+-----------------------+
|  1 | SIMPLE      | r     | ref    | res_status,res_category | res_status | 1       | const               |    1 | Using index condition |
|  1 | SIMPLE      | c     | eq_ref | PRIMARY                 | PRIMARY    | 4       | test.r.res_category |    1 | NULL                  |
+----+-------------+-------+--------+-------------------------+------------+---------+---------------------+------+-----------------------+

EXPLAIN
SELECT r.res_id, GROUP_CONCAT(s.s_name ORDER BY s.s_id SEPARATOR ', ') AS 'SchoolSubjects' 
FROM hre_resources AS r
INNER JOIN schoolsubjects_to_resource str ON str.sr_resid = r.res_id 
INNER JOIN schoolsubjects s ON s.s_id = str.sr_sid
WHERE r.res_status = 'Active' 
GROUP BY r.res_id
--------------

+----+-------------+-------+--------+---------------------------------+------------+---------+-----------------+------+--------------------------+
| id | select_type | table | type   | possible_keys                   | key        | key_len | ref             | rows | Extra                    |
+----+-------------+-------+--------+---------------------------------+------------+---------+-----------------+------+--------------------------+
|  1 | SIMPLE      | r     | ref    | PRIMARY,res_status,res_category | res_status | 1       | const           |    1 | Using where; Using index |
|  1 | SIMPLE      | str   | ref    | PRIMARY,sr_sid                  | PRIMARY    | 4       | test.r.res_id   |    1 | Using index              |
|  1 | SIMPLE      | s     | eq_ref | PRIMARY                         | PRIMARY    | 4       | test.str.sr_sid |    1 | NULL                     |
+----+-------------+-------+--------+---------------------------------+------------+---------+-----------------+------+--------------------------+
3 rows in set (0.00 sec)

--------------
EXPLAIN
SELECT r.res_id, GROUP_CONCAT(t.t_name ORDER BY t_id SEPARATOR ', ') AS 'Topics'
FROM hre_resources AS r
INNER JOIN topic_to_resource ttr ON ttr.rt_resourceid = r.res_id 
INNER JOIN topics t on t.t_id = ttr.rt_topicid 
WHERE r.res_status = 'Active' 
GROUP BY r.res_id
--------------

+----+-------------+-------+--------+---------------------------------+------------+---------+---------------------+------+--------------------------+
| id | select_type | table | type   | possible_keys                   | key        | key_len | ref                 | rows | Extra                    |
+----+-------------+-------+--------+---------------------------------+------------+---------+---------------------+------+--------------------------+
|  1 | SIMPLE      | r     | ref    | PRIMARY,res_status,res_category | res_status | 1       | const               |    1 | Using where; Using index |
|  1 | SIMPLE      | ttr   | ref    | PRIMARY,rt_topicid              | PRIMARY    | 4       | test.r.res_id       |    1 | Using index              |
|  1 | SIMPLE      | t     | eq_ref | PRIMARY                         | PRIMARY    | 4       | test.ttr.rt_topicid |    1 | NULL                     |
+----+-------------+-------+--------+---------------------------------+------------+---------+---------------------+------+--------------------------+
3 rows in set (0.00 sec)

--------------
EXPLAIN
SELECT r.res_id, GROUP_CONCAT(DISTINCT CONCAT(ch.ch_code, ':', ch.ch_title) ORDER BY ch.ch_id SEPARATOR ', ') AS 'Chapters'
FROM hre_resources AS r
INNER JOIN topic_to_resource ttr ON ttr.rt_resourceid = r.res_id 
INNER JOIN topics t on t.t_id = ttr.rt_topicid 
INNER JOIN topic_to_framework ttc on ttc.ft_topicid = t.t_id 
INNER JOIN ca_hss_frameworkchapters ch ON ch.ch_id = ttc.ft_frameworkid 
WHERE r.res_status = 'Active' 
GROUP BY r.res_id
--------------

+----+-------------+-------+--------+---------------------------------+------------+---------+-------------------------+------+--------------------------+
| id | select_type | table | type   | possible_keys                   | key        | key_len | ref                     | rows | Extra                    |
+----+-------------+-------+--------+---------------------------------+------------+---------+-------------------------+------+--------------------------+
|  1 | SIMPLE      | r     | ref    | PRIMARY,res_status,res_category | res_status | 1       | const                   |    1 | Using where; Using index |
|  1 | SIMPLE      | ttr   | ref    | PRIMARY,rt_topicid              | PRIMARY    | 4       | test.r.res_id           |    1 | Using index              |
|  1 | SIMPLE      | t     | eq_ref | PRIMARY                         | PRIMARY    | 4       | test.ttr.rt_topicid     |    1 | Using index              |
|  1 | SIMPLE      | ttc   | ref    | PRIMARY,ft_frameworkid          | PRIMARY    | 4       | test.ttr.rt_topicid     |    1 | Using index              |
|  1 | SIMPLE      | ch    | eq_ref | PRIMARY                         | PRIMARY    | 4       | test.ttc.ft_frameworkid |    1 | NULL                     |
+----+-------------+-------+--------+---------------------------------+------------+---------+-------------------------+------+--------------------------+
5 rows in set (0.00 sec)

--------------
EXPLAIN
SELECT r.res_id, GROUP_CONCAT(DISTINCT cs.cs_code ORDER BY cs.cs_id SEPARATOR ', ') AS 'ContentStandards'
FROM hre_resources AS r
INNER JOIN topic_to_resource ttr ON ttr.rt_resourceid = r.res_id 
INNER JOIN topics t on t.t_id = ttr.rt_topicid 
INNER JOIN topic_to_cs tcs on tcs.cst_topicid = t.t_id 
INNER JOIN ca_hss_contentstandards cs ON cs.cs_id = tcs.cst_contentstandardid 
WHERE r.res_status = 'Active' 
GROUP BY r.res_id
--------------

+----+-------------+-------+--------+---------------------------------+------------+---------+--------------------------------+------+--------------------------+
| id | select_type | table | type   | possible_keys                   | key        | key_len | ref                            | rows | Extra                    |
+----+-------------+-------+--------+---------------------------------+------------+---------+--------------------------------+------+--------------------------+
|  1 | SIMPLE      | r     | ref    | PRIMARY,res_status,res_category | res_status | 1       | const                          |    1 | Using where; Using index |
|  1 | SIMPLE      | ttr   | ref    | PRIMARY,rt_topicid              | PRIMARY    | 4       | test.r.res_id                  |    1 | Using index              |
|  1 | SIMPLE      | t     | eq_ref | PRIMARY                         | PRIMARY    | 4       | test.ttr.rt_topicid            |    1 | Using index              |
|  1 | SIMPLE      | tcs   | ref    | PRIMARY,cst_contentstandardid   | PRIMARY    | 4       | test.ttr.rt_topicid            |    1 | Using index              |
|  1 | SIMPLE      | cs    | eq_ref | PRIMARY                         | PRIMARY    | 4       | test.tcs.cst_contentstandardid |    1 | NULL                     |
+----+-------------+-------+--------+---------------------------------+------------+---------+--------------------------------+------+--------------------------+

以下是我为表格假设的DDL。如果您在原始问题中包含此内容，那将会很有帮助。

CREATE TABLE categories (
    c_id INT PRIMARY KEY,
    c_name VARCHAR(100) NOT NULL DEFAULT 'c_name'
);

CREATE TABLE hre_resources (
    res_id INT PRIMARY KEY,
    res_category INT NOT NULL,
    res_status ENUM('Active', 'Inactive') NOT NULL DEFAULT 'Active',
    res_type VARCHAR(100) NOT NULL DEFAULT 'type',
    res_title VARCHAR(100) NOT NULL DEFAULT 'title',
    res_filename VARCHAR(100) NOT NULL DEFAULT '',
    res_source VARCHAR(100) NOT NULL DEFAULT '',
    res_gradelevel_from VARCHAR(100) NOT NULL DEFAULT '',
    res_gradelevel_to VARCHAR(100) NOT NULL DEFAULT '',
    res_tags VARCHAR(100) NOT NULL DEFAULT '',
    res_description VARCHAR(100) NOT NULL DEFAULT '',
    res_onserver VARCHAR(100) NOT NULL DEFAULT '',
    res_favoriteaccts VARCHAR(100) NOT NULL DEFAULT '',
    res_CreatedOn DATE NOT NULL DEFAULT '2017-01-01',
    KEY (res_status),
    FOREIGN KEY (res_category) REFERENCES categories(c_id)
);

CREATE TABLE topics (
    t_id INT PRIMARY KEY,
    t_name VARCHAR(100) NOT NULL DEFAULT 't_name'
);

CREATE TABLE ca_hss_frameworkchapters (
    ch_id INT PRIMARY KEY,
    ch_title VARCHAR(100) NOT NULL DEFAULT 'ch_title',
    ch_code VARCHAR(100) NOT NULL DEFAULT 'ch_code'
);

CREATE TABLE ca_hss_contentstandards (
    cs_id INT PRIMARY KEY,
    cs_code VARCHAR(100) NOT NULL DEFAULT 'cs_code'
);

CREATE TABLE schoolsubjects (
    s_id INT PRIMARY KEY,
    s_name VARCHAR(100) NOT NULL DEFAULT 's_name'
);

CREATE TABLE topic_to_framework (
    ft_topicid INT NOT NULL,
    ft_frameworkid INT NOT NULL,
    PRIMARY KEY (ft_topicid, ft_frameworkid),
    FOREIGN KEY (ft_topicid) REFERENCES topics(t_id),
    FOREIGN KEY (ft_frameworkid) REFERENCES ca_hss_frameworkchapters(ch_id)
);

CREATE TABLE topic_to_resource (
    rt_resourceid INT NOT NULL,
    rt_topicid INT NOT NULL,
    PRIMARY KEY (rt_resourceid, rt_topicid),
    FOREIGN KEY (rt_resourceid) REFERENCES hre_resources (res_id),
    FOREIGN KEY (rt_topicid) REFERENCES topics(t_id)
);

CREATE TABLE topic_to_cs (
    cst_topicid INT NOT NULL,
    cst_contentstandardid INT NOT NULL,
    PRIMARY KEY (cst_topicid, cst_contentstandardid),
    FOREIGN KEY (cst_topicid) REFERENCES topics(t_id),
    FOREIGN KEY (cst_contentstandardid) REFERENCES ca_hss_contentstandards(cs_id)
);

CREATE TABLE schoolsubjects_to_resource (
    sr_resid INT NOT NULL,
    sr_sid INT NOT NULL,
    PRIMARY KEY (sr_resid, sr_sid),
    FOREIGN KEY (sr_resid) REFERENCES hre_resources(res_id),
    FOREIGN KEY (sr_sid) REFERENCES schoolsubjects(s_id)
);

这里有一个Python的例子，我将多个查询的结果合并在一起是什么意思。

import pprint
import MySQLdb
import MySQLdb.cursors

db = MySQLdb.connect(host="localhost", db="test", cursorclass=MySQLdb.cursors.DictCursor)
cur = db.cursor()

res_data = {}

sql = """SELECT r.res_id, r.res_status, r.res_type, r.res_category, r.res_title, r.res_filename, r.res_source, r.res_gradelevel_from, r.res_gradelevel_to, r.res_tags, r.res_description,  r.res_onserver, r.res_favoriteaccts, r.res_CreatedOn, c.c_name AS 'Categories' FROM hre_resources AS r INNER JOIN categories c ON c_id = r.res_category WHERE r.res_status = 'Active'"""
cur.execute(sql)
for row in cur.fetchall():
  res_data[row['res_id']] = row

sql = """SELECT r.res_id, GROUP_CONCAT(s.s_name ORDER BY s.s_id SEPARATOR ', ') AS 'SchoolSubjects' FROM hre_resources AS r INNER JOIN schoolsubjects_to_resource str ON str.sr_resid = r.res_id  INNER JOIN schoolsubjects s ON s.s_id = str.sr_sid WHERE r.res_status = 'Active' GROUP BY r.res_id"""
cur.execute(sql)
for row in cur.fetchall():
  res_data[row['res_id']].update(row)

sql = """SELECT r.res_id, GROUP_CONCAT(t.t_name ORDER BY t_id SEPARATOR ', ') AS 'Topics' FROM hre_resources AS r INNER JOIN topic_to_resource ttr ON ttr.rt_resourceid = r.res_id INNER JOIN topics t on t.t_id = ttr.rt_topicid WHERE r.res_status = 'Active' GROUP BY r.res_id"""
cur.execute(sql)
for row in cur.fetchall():
  res_data[row['res_id']].update(row)

sql = """SELECT r.res_id, GROUP_CONCAT(DISTINCT CONCAT(ch.ch_code, ':', ch.ch_title) ORDER BY ch.ch_id SEPARATOR ', ') AS 'Chapters' FROM hre_resources AS r INNER JOIN topic_to_resource ttr ON ttr.rt_resourceid = r.res_id INNER JOIN topics t on t.t_id = ttr.rt_topicid INNER JOIN topic_to_framework ttc on ttc.ft_topicid = t.t_id INNER JOIN ca_hss_frameworkchapters ch ON ch.ch_id = ttc.ft_frameworkid WHERE r.res_status = 'Active' GROUP BY r.res_id"""
cur.execute(sql)
for row in cur.fetchall():
  res_data[row['res_id']].update(row)

sql = """SELECT r.res_id, GROUP_CONCAT(DISTINCT cs.cs_code ORDER BY cs.cs_id SEPARATOR ', ') AS 'ContentStandards' FROM hre_resources AS r INNER JOIN topic_to_resource ttr ON ttr.rt_resourceid = r.res_id INNER JOIN topics t on t.t_id = ttr.rt_topicid INNER JOIN topic_to_cs tcs on tcs.cst_topicid = t.t_id INNER JOIN ca_hss_contentstandards cs ON cs.cs_id = tcs.cst_contentstandardid WHERE r.res_status = 'Active' GROUP BY r.res_id"""
cur.execute(sql)
for row in cur.fetchall():
  res_data[row['res_id']].update(row)

db.close()

pp = pprint.PrettyPrinter()
pp.pprint(res_data)

在我为每个表添加一行假数据后，我从上面的脚本中得到了这个输出：

{2L: {'Categories': 'c_name',
      'Chapters': 'ch_codech_title',
      'ContentStandards': 'cs_code',
      'SchoolSubjects': 's_name',
      'Topics': 't_name',
      'res_CreatedOn': datetime.date(2017, 1, 1),
      'res_category': 1L,
      'res_description': '',
      'res_favoriteaccts': '',
      'res_filename': '',
      'res_gradelevel_from': '',
      'res_gradelevel_to': '',
      'res_id': 2L,
      'res_onserver': '',
      'res_source': '',
      'res_status': 'Active',
      'res_tags': '',
      'res_title': 'title',
      'res_type': 'type'}}

Answer 2

首先在派生表中拉WHERE RES_Status = 'Active'。这可能会显着减小tmp表的大小，并可能显着缩小“创建排序索引”阶段。

然后专注于派生表。将它分开。需要多长时间？

对于56.7s部分，听起来有些设置太高了。请提供：

SHOW VARIABLES LIKE 'query%';
SHOW GLOBAL STATUS LIKE 'Qc%';

mySQL＆gt;＆gt;使用CONCAT，GROUP_CONCAT和多个JOINS进行非常慢的查询（63条记录为100秒）

2 个答案: