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What is a Database?
A database is a separate application that stores a collection of data. Each database has one or more distinct APIs for creating, accessing, managing, searching and replicating the data it holds.
Other kinds of data stores can also be used, such as files on the file system or large hash tables in memory but data fetching and writing would not be so fast and easy with those type of systems.
Nowadays, we use relational database management systems (RDBMS) to store and manage huge volume of data. This is called relational database because all the data is stored into different tables and relations are established using primary keys or other keys known as Foreign Keys.
A Relational DataBase Management System (RDBMS) is a software that ?
Enables you to implement a database with tables, columns and indexes.
Guarantees the Referential Integrity between rows of various tables.
Updates the indexes automatically.
Interprets an SQL query and combines information from various tables.
*Before we proceed to explain the MySQL database system, let us revise a few definitions related to the database.
* Database ? A database is a collection of tables, with related data.
* Table ? A table is a matrix with data. A table in a database looks like a simple spreadsheet.
* Column ? One column (data element) contains data of one and the same kind, for example the column postcode.
* Row ? A row (= tuple, entry or record) is a group of related data, for example the data of one subscription.
* Redundancy ? Storing data twice, redundantly to make the system faster.
* Primary Key ? A primary key is unique. A key value can not occur twice in one table. With a key, you can only find one row.
* Foreign Key ? A foreign key is the linking pin between two tables.