Databases

Relational databases were first designed as a way to represent data without redundancies so that they could be updated centrally and accessed throughout a system with only the relevant information visible to users. A Database Table consists of rows and columns with each row representing a particular thing, and each column representing a particular property of those things. For example, a database on a music collection might contain a database table containing data on all of the compact discs with columns labeled “Album Title,” “Artist,” “Year,” and “Record Label” and rows that represent each CD; a database table containing data on all of the vinyl records with the same row labels; and a database table containing data on all of the tapes with these same row labels. To access a particular set of data, a user could search one or more fields in a table. For instance, “select album_title, year from tapes where album_title = purple_rain;” would pull up the only the year and album title from any tapes whose album title was listed as Purple Rain. Just as it is possible to search many fields at the same time, it is also possible to search many tables at a time by. For instance, in the music example, it would be possible to pull up all of the records (not vinyl) in the collection regardless of the form by: “select * from tapes, CDs, vinyl records; “. This search would bring up all of the records.