MySQL8的数据库优化讲义详解

发布时间：2023-08-18 15:23:11 所属栏目：MySql教程来源：

导读：下文内容主要给大家带来MySQL8的数据库优化讲义，这里所讲到的知识，与书籍略有不同，都是亿速云专业技术人员在与用户接触过程中，总结出来的，具有一定的经验分享价值，希望给广大读者带来帮助。

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下文内容主要给大家带来MySQL8的数据库优化讲义，这里所讲到的知识，与书籍略有不同，都是亿速云专业技术人员在与用户接触过程中，总结出来的，具有一定的经验分享价值，希望给广大读者带来帮助。

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select dept_name from dept_emp join employees on dept_emp.emp_no=employees.emp_no join departments on departments.dept_no=dept_emp.dept_no where employees.first_name='Aamer';

EXPLAIN format=JSON select dept_name from dept_emp join employees on dept_emp.emp_no=employees.emp_no join departments on departments.dept_no=dept_emp.dept_no where employees.first_name='Aamer';

mysql> select connection_id();

+-----------------+

| connection_id() |

+-----------------+

| 30 |

+-----------------+

1 row in set (0.01 sec)

mysql> explain format=json for connection 30\G

ERROR 3012 (HY000): EXPLAIN FOR CONNECTION command is supported only for SELECT/UPDATE/INSERT/DELETE/REPLACE

mysql> pager grep rows

mysql> SELECT e.emp_no,salary from salaries s join employees e on s.emp_no=e.emp_no where first_name='Adam';

2384 rows in set (0.24 sec)

mysql> pager

Default pager wasn't set, using stdout.

MySQL8的数据库优化讲义

mysqlslap

mysqlslap 对于模拟多个用户同时对 MySQL 发起“进攻”提供了方便。同时详细的提供了“高负荷*** MySQL”的详细数据报告。

#mysqlslap -uroot -p --create-schema=employees --query="SELECT e.emp_no,salary from salaries s join employees e on s.emp_no=e.emp_no where first_name='Adam';" -c 100 -i 100

Enter password:

Benchmark

Average number of seconds to run all queries: 0.995 seconds

Minimum number of seconds to run all queries: 0.876 seconds

Maximum number of seconds to run all queries: 1.155 seconds

Number of clients running queries: 100

Average number of queries per client: 1

#mysqlslap -uroot -p --auto-generate-sql --concurrency=50,100 --number-of-queries=1000 -i 5 --debug-info

Enter password:

Benchmark

Average number of seconds to run all queries: 0.148 seconds

Minimum number of seconds to run all queries: 0.148 seconds

Maximum number of seconds to run all queries: 0.148 seconds

Number of clients running queries: 50

Average number of queries per client: 20

Benchmark

Average number of seconds to run all queries: 0.143 seconds

Minimum number of seconds to run all queries: 0.143 seconds

Maximum number of seconds to run all queries: 0.143 seconds

Number of clients running queries: 100

Average number of queries per client: 10

mysqlslap -uroot -p --auto-generate-sql --only-print

#mysqlslap -uroot -p --concurrency=50,100,200 --iterations=1 --number-int-cols=4 --number-char-cols=35 \

--auto-generate-sql --auto-generate-sql-add-autoincrement --auto-generate-sql-load-type=mixed --engine=innodb --number-of-queries=200

Enter password:

Benchmark

Running for engine innodb

Average number of seconds to run all queries: 0.042 seconds

Minimum number of seconds to run all queries: 0.042 seconds

Maximum number of seconds to run all queries: 0.042 seconds

Number of clients running queries: 50

Average number of queries per client: 4

Benchmark

Running for engine innodb

Average number of seconds to run all queries: 0.022 seconds

Minimum number of seconds to run all queries: 0.022 seconds

Maximum number of seconds to run all queries: 0.022 seconds

Number of clients running queries: 100

Average number of queries per client: 2

Benchmark

Running for engine innodb

Average number of seconds to run all queries: 0.515 seconds

Minimum number of seconds to run all queries: 0.515 seconds

Maximum number of seconds to run all queries: 0.515 seconds

Number of clients running queries: 200

Average number of queries per client: 1

#mysqlslap -uroot -p --delimiter=";" --create="CREATE TABLE a (b int);INSERT INTO a VALUES (23)" --query="SELECT * FROM a" --concurrency=50 --iterations=200

Enter password:

Benchmark

Average number of seconds to run all queries: 0.002 seconds

Minimum number of seconds to run all queries: 0.002 seconds

Maximum number of seconds to run all queries: 0.007 seconds

Number of clients running queries: 50

Average number of queries per client: 1

mysqlslap --concurrency=5 --iterations=5 --query=query.sql --create=create.sql --delimiter=";"

参考：https://my.oschina.net/moooofly/blog/152547

where、order by、group by、表连接都会使用到索引

主键的选择：

1、唯一非空

2、尽量的小，因为所有的二级索引都会存储主键

3、选择一个单调自增的键，物理行是按照主键排序的

alter table employees add [unqiue] index idx_name(first_name(10));

alter table employees drop index idx_name;

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