Follow the step-by-step learning method of MySQL optimization using the heat-resistance protocol.

In the second set

1. Show status like 'com % 'is equivalent to show status session like 'com %' for a hundred years -- display the current console status

Show global status like 'com % '-- displays the number of times the database has been started and queried.

Show session status like 'com _ select ';

Show status like 'uptime' -- how long it has been started
Show status like 'connections' -- number of connections

Slow_queries slow Query Count (default value: 10)

For the MyISAM database, it must be cleaned regularly.
Optimize table name. Otherwise, the deletion record is not cleared.
Order by null disable sorting
Use join instead of subquery
In finance, you can use a certain number of points to place decimal data. Do not use float for a period of time because float will lose data. Such as float (10, 5 ),
In the date type, numeric values are used instead of datastmp.