About MySQL four kinds of engines

The database engine you can use depends on how MySQL was compiled when it was installed. To add a new engine, you must recompile MySQL. By default, MySQL supports three engines: ISAM, MyISAM, and heap. Two other types of InnoDB and Berkley (BDB) are also often available.

ISAM

ISAM is a well-defined and time-tested form of data management that, at design time, takes into account that the number of times the database is queried is much larger than the number of updates. As a result, ISAM performs read operations quickly and does not consume large amounts of memory and storage resources. The two main disadvantages of ISAM are that it does not support transactional processing or fault tolerance: If your hard drive crashes, the data file cannot be recovered. If you are using ISAM in mission-critical applications, you must always back up all of your real-time data, and with its replication features, MySQL can support such a backup application.

MYISAM

MyISAM is the ISAM extended format for MySQL and the default database engine. In addition to providing a number of functions for index and field management that are not available in ISAM, MyISAM also uses a form-locking mechanism to optimize multiple concurrent read and write operations. The cost is that you need to run the Optimize Table command frequently to restore the space wasted by the updated mechanism. MyISAM also has some useful extensions, such as the Myisamchk tool for repairing database files and the Myisampack tool for recovering wasted space.

MyISAM emphasizes fast read operations, which may be the main reason why MySQL is so popular with Web development: in Web development, the bulk of your data operations are read operations. Therefore, most web hosting providers and internet platform providers only allow the use of the MyISAM format.

HEAP

The heap allows temporary tables that reside only in memory. Residing in memory makes the heap faster than ISAM and MyISAM, but the data it manages is unstable, and if it is not saved before shutdown, all data will be lost. The heap does not waste a lot of space when the data rows are deleted, and the heap table is useful when you need to select and manipulate data using the Select expression. Remember to delete the table after you have finished using the table.

InnoDB and Berkleydb

The InnoDB and Berkleydb (BDB) database engine is a direct product of the technology that makes MySQL flexible, which is the mysql++ API. Every challenge you face when using MySQL comes from the ISAM and the MYIASM database engine does not support transactional processing or foreign keys. Although much slower than ISAM and MyISAM engines, InnoDB and BDB include support for transaction processing and foreign keys, which are not available in the top two engines for two points. As mentioned earlier, if your design requires accesses than either or both of these features, you will be forced to use one of the latter two engines.

About MySQL four kinds of engines