mysql - 需要优化 MySQL 查询

Question

我有一个需要 33 秒的查询有没有更好的方法来重写它，我怎样才能将它转换为程序

select ut.templateId,
(
case 
when ut.reportTypeId=4 then 'Account'
when ut.reportTypeId=5 then 'Campaign' 
when ut.reportTypeId=6 then 'AdGroup' 
when ut.reportTypeId=7 then 'Ad'
when ut.reportTypeId=8 then 'Keyword' 
end
)as ReportType ,
ur.reportId,
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) < 5 then a.reportId else 0 end) as '<5secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 5 and 10 then a.reportId else 0 end) as '5-10secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 11 and 20 then a.reportId else 0 end) as '11-20secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 21 and 30 then a.reportId else 0 end) as '21-30secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 31 and 60 then a.reportId else 0 end) as '31-60secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 61 and 120 then a.reportId else 0 end) as '61-120secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 121 and 1800 then a.reportId else 0 end) as '2-30mins',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) > 1800 then a.reportId else 0 end) as '>30mins'
from

(select reportId,createdTS from T_ReportMonitor where status='EndSP')a,
(select reportId,createdTS from T_ReportMonitor where status='BeginSP')b,
(select templateId,reportTypeId,reportConsoleType from T_UserTemplate) ut,
(select reportId,templateId,createdTS,modifiedTS,isDeleted from T_UserReport) ur

where a.reportId=b.reportId 
and date(ur.createdTS) = 20120731
and ut.templateId=ur.templateId 
and reportConsoleType in ('Adser','APIAdser') 
and ur.isDeleted=false
and a.reportId=ur.reportId 
and ur.reportId!=313509 AND ur.reportId!=313510 AND ur.reportId!=313511 AND ur.reportId!=313512 AND ur.reportId!=313509 AND ur.reportId!=313510 AND ur.reportId!=313511 AND ur.reportId!=313512 AND ur.reportId!=313520;

查询的解释结果为

+----+-------------+-----------------+------+---------------+------+---------+------+--------+--------------------------------+
| id | select_type | table           | type | possible_keys | key  | key_len | ref  | rows   | Extra                          |
+----+-------------+-----------------+------+---------------+------+---------+------+--------+--------------------------------+
|  1 | PRIMARY     | <derived2>      | ALL  | NULL          | NULL | NULL    | NULL |  20071 |                                |
|  1 | PRIMARY     | <derived3>      | ALL  | NULL          | NULL | NULL    | NULL |  20072 | Using where; Using join buffer |
|  1 | PRIMARY     | <derived5>      | ALL  | NULL          | NULL | NULL    | NULL | 148591 | Using where; Using join buffer |
|  1 | PRIMARY     | <derived4>      | ALL  | NULL          | NULL | NULL    | NULL | 154030 | Using where; Using join buffer |
|  5 | DERIVED     | T_UserReport    | ALL  | NULL          | NULL | NULL    | NULL | 124008 |                                |
|  4 | DERIVED     | T_UserTemplate  | ALL  | NULL          | NULL | NULL    | NULL | 151745 |                                |
|  3 | DERIVED     | T_ReportMonitor | ALL  | NULL          | NULL | NULL    | NULL |  60849 | Using where                    |
|  2 | DERIVED     | T_ReportMonitor | ALL  | NULL          | NULL | NULL    | NULL |  60849 | Using where                    |
+----+-------------+-----------------+------+---------------+------+---------+------+--------+--------------------------------+

我有在 where 子句和任何其他比较中使用的列上的键，但它们都没有在查询中使用，是不是因为它们是派生查询。

Answer 1

它们是派生查询，但我认为没有理由这样做。

例如，考虑reportId每一行中的 总是相同的。那么总是参考reportId驱动表是有利的（MySQL应该足够聪明，可以自己做）。

例如 a 和 b 表可以像这样连接

FROM
T_UserReport AS ur
JOIN T_ReportMonitor AS a ON (a.reportId = ur.reportId AND a.status = 'EndSP')
JOIN T_ReportMonitor AS b ON (b.reportId = ur.reportId AND b.status = 'BeginSP')

然后T_ReportMonitor只需要一个索引status和reportId：

CREATE INDEX ut_ndx ON T_ReportMonitor ( status, reportId, createdTS )

这允许 MySQL 立即为 a 选择 EndSP 条目，并为 JOIN 提供方便的 reportId 列；完成此操作后，它还发现自己具有用于查询的 createdTS。（更大的）数据表本身根本不需要访问。

同样的概念也适用于其他表。如果你

• 加入第 1 列，
• 在 column2 [AND column2a...]值上有一个简单的 WHERE 过滤子句，
• 查询正文中只需要 column3
• 并且该表明显大于迄今为止命名的三列，

那么你会发现这样做是有利的

JOIN table AS alias ON (alias.column1 = ... AND alias.column2 = 'filter value')

并有一个索引，例如

CREATE INDEX table_ndx ON table ( column2, column1, column3 )

Answer 2

您的查询的主要问题是它使用子查询。MySQL 不能在子查询上使用索引，因为它基本上会在内存（或磁盘）中为您的子查询创建一个新表。尝试进行连接。

试试这个

select ut.templateId,
(
case 
when ut.reportTypeId=4 then 'Account'
when ut.reportTypeId=5 then 'Campaign' 
when ut.reportTypeId=6 then 'AdGroup' 
when ut.reportTypeId=7 then 'Ad'
when ut.reportTypeId=8 then 'Keyword' 
end
)as ReportType ,
ur.reportId,
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) < 5 then a.reportId else 0 end) as '<5secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 5 and 10 then a.reportId else 0 end) as '5-10secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 11 and 20 then a.reportId else 0 end) as '11-20secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 21 and 30 then a.reportId else 0 end) as '21-30secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 31 and 60 then a.reportId else 0 end) as '31-60secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 61 and 120 then a.reportId else 0 end) as '61-120secs',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) between 121 and 1800 then a.reportId else 0 end) as '2-30mins',
(case when timestampdiff(SECOND,b.createdTS,a.createdTS) > 1800 then a.reportId else 0 end) as '>30mins'
from
T_ReportMonitor as a JOIN T_ReportMonitor as b ON (a.reportId=b.reportId) JOIN  T_UserReport as ur ON (a.reportId=ur.reportId) JOIN T_UserTemplate as ut ON (ut.templateId=ur.templateId)
WHERE a.status='EndSP' AND b.status='BeginSP'
and date(ur.createdTS) = 20120731
and reportConsoleType in ('Adser','APIAdser') 
and ur.isDeleted=false
and ur.reportId NOT IN (313509,313510,313511,313512,313509,313510,313511,313512,313520);

确保 T_ReportMonitor.reportId、T_ReportMonitor.status 和 T_UserReport.reportId 上有一个键。

还有一件事会降低您的查询质量。您在 where 中使用函数：

date(ur.createdTS)

这意味着 MySQL 将不得不处理每一行以查看该函数的结果。这甚至可能被证明是最大的性能提升。尝试使该字段成为日期字段（或创建新的日期字段）或使用类似

WHERE ur.createdTS>='2012-07-31 00:00:00' AND ur.createdTS<='2012-07-31 23:95:59'