SQL(3)---Relational Database Management System(RDBMS)

Relational Database Management System

------A relational database management system (RDBMS) is a program that allows you to create, update, and administer a relational database. Most relational database management systems use the SQL language to access the database. 

• A database is a set of data stored in a computer. This data is usually structured in a way that makes the data easily accessible. 
• A relational database is a type of database. It uses a structure that allows us to identify and access data in relation to another piece of data in the database. Often, data in a relational database is organized into tables. 

Tables: Rows and Columns

• Tables can have hundreds, thousands, sometimes even millions of rows of data. These rows are often called records.
• Tables can also have many columns of data. Columns are labeled with a descriptive name (say, age for example) and have a specific data type.

SQL syntax may differ slightly depending on which RDBMS you are using:

SQLite is a popular open source SQL database. It can store an entire database in a single file. One of the most significant advantages this provides is that all of the data can be stored locally without having to connect your database to a server. It is a popular choice for databases in cellphones, PDAs, MP3 players, set-top boxes, and other electronic gadgets.

MySQL is the most popular open source SQL database. It is typically used for web application development, and often accessed using PHP. The main advantages of MySQL are that it is easy to use, inexpensive, reliable (has been around since 1995), and has a large community of developers who can help answer questions. Some of the disadvantages are that it has been known to suffer from poor performance when scaling, open source development has lagged since Oracle has taken control of MySQL, and it does not include some advanced features that developers may be used to. 

PostgreSQL is an open source SQL database that is not controlled by any corporation. It is typically used for web application development. PostgreSQL shares many of the same advantages of MySQL. It is easy to use, inexpensive, reliable and has a large community of developers. It also provides some additional features such as foreign key support without requiring complex configuration. The main disadvantage of PostgreSQL is that it is slower in performance than other databases such as MySQL. It is also less popular than MySQL which makes it harder to come by hosts or service providers that offer managed PostgreSQL instances. 

Oracle DB (Oracle Corporation owns Oracle Database, and the code is not open sourced.) is for large applications, particularly in the banking industry. Most of the world’s top banks run Oracle applications because Oracle offers a powerful combination of technology and comprehensive, pre-integrated business applications, including essential functionality built specifically for banks. The main disadvantage of using Oracle is that it is not free to use like its open source competitors and can be quite expensive.