This article is an introduction to working with database engines in MySQL.
Database engines provide the underlying functionality for MySQL to work with and process data.
The two most common and popular MySQL database engines are MyISAM and InnoDB. MyISAM is the default engine for MySQL for versions earlier than 5.5.5, and functions well in most scenarios. However, depending on your needs, there are situations where another database engine, such as InnoDB, may be the better choice. For example, InnoDB supports transactions, whereas MyISAM does not. InnoDB also provides support for foreign keys, whereas MyISAM does not.
If you have root access to your server, you have complete control over how and when MySQL uses the various database engines. You can change the default database engine, change a specific table's database engine, and more.
To determine the default database engine for your installation, type the following command at the mysql> prompt:
A list of supported engines appears, along with a brief description and the supported features for each engine. The default database engine is marked DEFAULT in the Support column.
You can change the default database engine for your MySQL installation. After you do this, all new tables that you create will use the new database engine (unless you explicitly set the engine during table creation).
To change the default database engine, follow these steps:
Add or modify the following line in the [mysqld] section. Replace ENGINE with the name of the engine that you want to use as the default:
If you are enabling the InnoDB database engine, depending on your Linux distribution you may have to disable the following line in the my.cnf file:
To do this, just add a pound sign (#) to the beginning of the line, as follows:
Restart the MySQL server using the appropriate command for your Linux distribution:
service mysqld restart
For Debian and Ubuntu, type:
service mysql restart
To determine which engine a database table is currently using, type the following command at the mysql> prompt. Replace database with the name of the database that you want to check:
SELECT TABLE_NAME, ENGINE FROM information_schema.TABLES where TABLE_SCHEMA = 'database';
This command displays a list of every table in the database, along with the engine each table is using.
You can change the database engine for a table that already exists. For example, the following SQL statement shows how to modify a table named myTable to use the InnoDB engine:
ALTER TABLE myTable ENGINE = InnoDB;
When you create a table in a database, you can explicitly set its database engine (otherwise, MySQL uses the default database engine during table creation). For example, the following SQL statement shows how to create a table named myTable that uses the MyISAM database engine:
CREATE TABLE myTable ( id INT NOT NULL AUTO_INCREMENT, PRIMARY KEY (id), data VARCHAR(20) NOT NULL ) ENGINE MyISAM;
Simiarly, to create a table that uses the InnoDB database engine, you could use the following SQL statement:
CREATE TABLE myTable ( id INT NOT NULL AUTO_INCREMENT, PRIMARY KEY (id), data VARCHAR(20) NOT NULL ) ENGINE InnoDB;