In the broadest definition, a database is anything that collects and organizes data. A spreadsheet holding customer bookings is a database, and so is a plain-text file containing flight schedule data. Plain-text data itself can be stored in a variety of formats, including XML and CSV.
Professionally, however, when one refers to a “database” they likely are referring to a relational database management system (RDBMS). This term may sound technical and intimidating, but an RDBMS is simply a type of database that holds one or more tables that may have relationships to each other.
A table should be a familiar concept. It has columns and rows to store data, much like a spreadsheet. These tables can have relationships to each other, such as an
ORDER table that refers to a
CUSTOMER table for customer information.
For example, suppose we have an
ORDER table with a field called
CUSTOMER_ID (Figure 2-1).
We can reasonably expect there to be another table, maybe called
CUSTOMER (Figure 2-2), which holds the customer information for each
When we go through the
ORDER table, we can use the
CUSTOMER_ID to look up the customer information ...