A key value can not occur twice in one table. Redundancy − Storing data twice, redundantly to make the system faster. Row − A row (= tuple, entry or record) is a group of related data, for example the data of one subscription. A table in a database looks like a simple spreadsheet.Ĭolumn − One column (data element) contains data of one and the same kind, for example the column postcode. Interprets an SQL query and combines information from various tables.īefore we proceed to explain the MySQL database system, let us revise a few definitions related to the database.ĭatabase − A database is a collection of tables, with related data. Guarantees the Referential Integrity between rows of various tables. 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.Ī Relational DataBase Management System (RDBMS) is a software that −Įnables you to implement a database with tables, columns and indexes. Nowadays, we use relational database management systems (RDBMS) to store and manage huge volume of data. 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. Each database has one or more distinct APIs for creating, accessing, managing, searching and replicating the data it holds. A database is a separate application that stores a collection of data.
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