Cloud Database Development — The Basics - Beginning iOS Cloud and Database Development - page 5

The Database File
A database file is defined as a collection of related data. A database contains tables with each
family of data. A database file may be composed of a complete list of individuals on a mailing list,
including their addresses and telephone numbers. Files are frequently categorized by the purpose
or application for which they are intended. Some common examples include mailing lists, customer
files, inventory files, or document files.
Organizations and individuals use databases to bring independent sources of data together and
store them electronically. Thus, a database is composed of related files that are consolidated,
organized, and stored together. One collection of related files might pertain to employee information.
Another collection of related files might contain the items in the inventory. As you'll see in the next
section, the database model consists of multiple tables.
The Relational Database
Relational databases work on the principle that each table has a key field that uniquely identifies
each row, and that these key fields can be used to connect one table of data to another. Thus,
one table might have a row consisting of a customer account number as the key field along with
address and telephone number. The customer account number in this table could be linked to
another table of data that also includes customer account number (a key field), but in this case,
contains information about product returns, including an item number (another key field). This key
field can be linked to another table that contains item numbers and other product information, such
as production location, color, quality control person, and other data. Therefore, using this database,
customer information can be linked to specific product information.
The relational database has become quite popular for two reasons. First, relational databases can be
used with little or no training. Second, database entries can be modified without redefining the entire
structure. The downside of using a relational database is that searching for data can take more time
than if other methods are used. Figure 1-3 shows an example relational design.