View source for Column (database)

{{Short description|Data values in computer science}}
{{more citations needed|date=September 2016}}

In a [[relational database]], a '''column''' is a set of [[data]] values of a particular [[datatype|type]], one value for each [[Row (database)|row]] of a [[table (database)|table]].<ref name="ColumnOther">The term "column" also has equivalent applications in other, more generic contexts. See e.g., [[Flat file database]], [[Table (information)]].</ref> A column may contain text values, numbers, or even pointers to files in the operating system.<ref>{{Cite web|title = Columnar databases in a big data environment|url = http://www.dummies.com/how-to/content/columnar-databases-in-a-big-data-environment.html|website = dummies.com (Big dummies book)|access-date = 2015-11-05}}</ref> Columns typically contain [[Primitive data type|simple types]], though some relational database systems allow columns to contain more complex data types, such as whole documents, images, or even video clips.<ref>{{Cite web|title = What is Database Column? - Definition from Techopedia|url = https://www.techopedia.com/definition/8/database-column|website = Techopedia.com|access-date = 2015-11-05}}</ref>{{better source needed|date=June 2022}} A column can also be called an '''attribute'''.

Each row would provide a data value for each column and would then be understood as a single structured data value. For example, a database that represents company contact information might have the following columns: ID, Company Name, Address Line 1, Address Line 2, City, and Postal Code. More formally, a row is a tuple containing a specific value for each column,<ref>{{Cite news |last=Rosenberg |first=Burton |title=Relational Databases |work=University of Miami |url=https://www.cs.miami.edu/home/burt/learning/Csc598.073/notes/reldb.html |access-date=2021-02-26}}</ref> for example: (1234, 'Big Company Inc.', '123 East Example Street', '456 West Example Drive', 'Big City', 98765).

== Field ==
{{further|Field (computer science)}}
The word 'field' is normally used interchangeably with 'column'.<ref>{{Cite web|title = An introduction to databases|url = http://www.ucl.ac.uk/archaeology/cisp/database/manual/node1.html|website = www.ucl.ac.uk|access-date = 2015-11-05}}</ref> However, database perfectionists tend to favor using 'field' to signify a specific cell of a given row. {{citation needed|date=April 2018}} This is to enable accuracy in communicating with other developers. Columns (really column names) being referred to as field names (common for each row/record in the table). Then a field refers to a single storage location in a specific record (like a cell) to store one value (the field value). The terms record and field come from the more practical field of database usage and traditional [[Dbms|DBMS]] system usage (This was linked into business like terms used in manual databases e.g. filing cabinet storage with records for each customer). The terms row and column come from the more theoretical study of relational theory.

Another distinction between the terms 'column' and 'field' is that the term 'column' does not apply to certain databases, for instance [[Key–value database|key-value stores]], that do not conform to the traditional [[relational database]] structure.<ref name="{{Cite news}}...">{{Cite web |last=Drake |first=Mark |date=August 9, 2019 |title=A Comparison of NoSQL Database Management Systems and Models |url=https://www.digitalocean.com/community/tutorials/a-comparison-of-nosql-database-management-systems-and-models |access-date=2021-02-26 |website=Digital Ocean |language=en}}</ref>

== See also ==
* [[Column-oriented DBMS]], optimization for column-centric queries
* [[Column (data store)]], a similar object used in [[distributed data store]]s
* [[Row (database)]]
* [[SQL]]
* [[Query language]]
* [[Column groups and row groups]]

== References ==
{{Reflist|refs=http://searchdatamanagement.techtarget.com/definition/columnar-database}}

{{Databases}}
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[[Category:Data modeling]]
[[Category:Database management systems]]