MySQL related knowledge

Database Engine

1. View Database Engine

show engines;

As you can see from the above figure, the InnoDB database supports transactions, row-level locks, foreign keys, savepoints

2. Modify the database engine
   Description: Add default-storage-engine=INNODB
under the mysqld module of the configuration file

After restarting the database service, check the engine information to see if the default engine is modified successfully

Database import and export

1. Database export

   Description: dbname is the name of the database to be exported

# Log in to the server where mysql is located to export locallymysqldump -uroot -p111111 dbname >dbname.db.sql# Export the remote mysql database to the local hostmysqldump -uroot -p111111 -h 192.168.72.201 test >test.db.sql

2. Database Import

# Log in to the server where mysql is located to import locallymysql -uroot -p111111 dbname <dbname.db.sql# Import from the local, import the device into the remote specified databasemysql -uroot -p111111 -h 192.168.72.201 test <test.db.sql

Slow query related

1. View slow query information

show variables like "%slow%";

2. Enable slow query

set global slow_query_log=on;

How to deal with forgotten MySQL database password

1. Add skip-grant-tables under the mysqld module

   sed -i '1a skip-grant-tables' /etc/my.cnf

   

2. Restart the database service, and then you can log in without password through the mysql command

   

3. Change the user's password

   # Change the passwordupdate mysql.user set password=password('123456') where user='root';# Inquireselect host,user,password from mysql.user;

   

4. Delete the mysqld module and add the skip-grant-tables field, restart the database service, and log in with the new password

   # delete skip-grant-tables fieldsed -i '2d' /etc/my.cnf# Restart mysql database servicesystemctl restart mariadb# Login with new passwordmysql -uroot -p123456