Column (database)

In a relational database, a column is a set of data values of a particular simple type, one value for each row of the database.[1] A column may contain text values, numbers, or even pointers to files in the operating system.[2] Some relational database systems allow columns to contain more complex data types; whole documents, images or even video clips are examples.[3] A column can also be called an attribute.

An example of output columns from a Postgres database.

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, each row can be interpreted as a relvar, composed of a set of tuples, with each tuple consisting of the relevant column and its value, for example, the tuple ('Address 1', '12345 West Example Street').

Field

The word 'field' is normally used interchangeably with 'column'.[4] However, database perfectionists tend to favor using 'field' to signify a specific cell of a given row. 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 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.

See also

References
  1. The term "column" also has equivalent applications in other, more generic contexts. See e.g., Flat file database, Table (information).
  2. "Columnar databases in a big data environment". dummies.com (Big dummies book). Retrieved 2015-11-05.
  3. "What is Database Column? - Definition from Techopedia". Techopedia.com. Retrieved 2015-11-05.
  4. "An introduction to databases". www.ucl.ac.uk. Retrieved 2015-11-05.
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