MySql :

MySQL is an open source relational database management system (RDBMS) that uses Structured Query Language (SQL), the most popular language for adding, accessing, and processing data in a database.

* The primary key of a relational table uniquely identifies each record in the table.
* SQL statements are CASE INSENSITIVE i.e, it may be written in uppercase or lowercase. For good practice use upper case always.

DATABASE ENGINES

Data in MySQL is stored using different engine. Each of these engine follows different storage mechanisms, indexing facilities, locking levels and ultimately provide a range of different capabilities. By choosing a engine you can gain additional speed or functionality benefits that will improve the overall functionality of your application.


1.ISAM :

ISAM is a well-defined, time-tested method of managing data tables, designed with the idea that a database will be queried far more often than it will be updated. As a result, ISAM performs very fast read operations and is very easy on memory and storage resources. The two main downsides of ISAM are that it doesn't support transactions and isn't fault-tolerant: If your hard drive crashes, the data files will not be recoverable. If you're using ISAM in a mission-critical application, you'll want to have a provision for constantly backing up all your live data, something MySQL supports through its capable replication features.

2.MYISAM :

MyISAM is MySQL's extended ISAM format and default database engine. In addition to providing a number of indexing and field management functions not available in ISAM, MyISAM uses a table-locking mechanism to optimize multiple simultaneous reads and writes. MyISAM, with its emphasis on speedy read operations, is probably the major reason MySQL is so popular for Web development, where the vast majority of the data operations you'll be carrying out are read operations.

3.INNODB :

The InnoDB database engines are direct products of the technology that makes MySQL so flexible, Almost every challenge you're likely to face when using MySQL stems directly from the fact that the ISAM and MyISAM database engines aren't transactional and lack foreign-key support. Although much slower than the ISAM and MyISAM engines, InnoDB include the transactional and foreign-key support missing from the former two choices. As such, if your design requires either or both of these features, you're actually compelled to use one of these two choices.