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Candidate Key - A candidate key identifies a set of attributes in an entity that can uniquely identify a record (tuple). Generally, a candidate key will be implemented in a physical design as a primary key or a unique key.

Cascading Style Sheets (CSS) - Cascading Style Sheets is a style sheet language that is used to format HTML and XML. CSS is designed to separate a web page\'s layout and presentation from the data contained with in it.

Coherence - Oracle Coherence is a distributed memory cache for applications. Coherence replicates data from one to another ensuring availablity of data.

Column - an attribute of a table. A column is also frequently referred to as a field.

Columnar Database - See Also: Columnar Storage

Columnar Storage - Columnar storage in a database refers to a database that stores data in columns instead of rows. In some columnar storage engines, it also means that data is compressed in columns allowing much greater compression that data stored across rows (as columnar data is more likely to have duplicate values). Columnar storage is available in Sybase IQ, Vertica, Paraccel, and LucidDB amongst others. More and more are coming on the scene daily. Some columnar storage engines are set up through indexing schemes such as B-Tree and Bitmaps. Other storage engines actually place data on disk in matching, row based locations allowing one to skip the issues that come with multiple indexes. Some columnar database also store duplicate versions of the data, pre-sorted in various orders to allow faster retrieval.

Contact: Lewis Cunningham
lewisc@databasewisdom.com

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