Changes

== Terminology ==

== Terminology ==

Data in a database is organized by means of a <i>key</i> which allows sorting the data for quick lookup and retrieval of the information.  For instance, a library's card catalog can be organized by title, or by author and title.  In the first case, the title is the key.  In the second case, the combined author and title are the key.  Each card represents a <i>record</i> of information, which contains <i>fields</i> of information related to the key for that record (such as the publisher, copyright year, and a brief description, in addition to the author and title).  Because a physical database can only be effectively sorted for one key, a card catalog had to be duplicated, with each duplicate being sorted differently (one by author name, one by title, etc).  In database terminology, each different sorted collection is called a [[database table|table]], and the collection of all related tables is collectively called a database.

Data in a database is organized by means of a ''key'' which allows sorting the data for quick lookup and retrieval of the information.  For instance, a library's card catalog can be organized by title, or by author and title.  In the first case, the title is the key.  In the second case, the combined author and title are the key.  Each card represents a ''record'' of information, which contains ''fields'' of information related to the key for that record (such as the publisher, copyright year, and a brief description, in addition to the author and title).  Because a physical database can only be effectively sorted for one key, a card catalog had to be duplicated, with each duplicate being sorted differently (one by author name, one by title, etc.).  In database terminology, each different sorted collection is called a [[database table|table]], and the collection of all related tables is collectively called a database.

The size of the database is the number of records it contains.  This can be from 1 to billions of records.  Implementation of a database in software provides several advantages over a physical database: 1) much smaller physical size, especially for large databases, 2) much faster lookup of information, 3) the ability to have multiple keys applied to the same data, rather than a separate table for the way each table is keyed, 4) the ability to quickly apply changes across multiple (or all) records.

The size of the database is the number of records it contains.  This can be from 1 to billions of records.  Implementation of a database in software provides several advantages over a physical database: 1) much smaller physical size, especially for large databases, 2) much faster lookup of information, 3) the ability to have multiple keys applied to the same data, rather than a separate table for the way each table is keyed, 4) the ability to quickly apply changes across multiple (or all) records.

=== Relational ===

=== Relational ===

The most commonly used organization is ''relational'', in which the data in the [[database table|table]]s are organized as rows (records) and columns (fields).  Relational databases differ from other database organizations in that each row has the exact same fields as every other row for a given table, although some fields may be unused for some rows.  Keys are defined as being one or more columns and data lookups using keys is much faster than lookups based on non-key fields.  Fields in one table can be associated with related fields in other tables, hence the name "relational", and data can be looked up by simple <i>join</i> operations that returns records from several tables based on these related fields.

The most commonly used organization is ''relational'', in which the data in the [[database table|table]]s are organized as rows (records) and columns (fields).  Relational databases differ from other database organizations in that each row has the exact same fields as every other row for a given table, although some fields may be unused for some rows.  Keys are defined as being one or more columns and data lookups using keys is much faster than lookups based on non-key fields.  Fields in one table can be associated with related fields in other tables, hence the name "relational", and data can be looked up by simple ''join'' operations that returns records from several tables based on these related fields.

[[Relational database]]s have become popular due to high speed.   

[[Relational database]]s have become popular due to high speed.