Column

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Column

A column is part of a database table, and is also known as an attribute or field. Columns list the names of the individual fields in a table.

A column describes an atomic or indivisible basic piece of information in the database, clearly differentiated from other data, e.g. zip code (and not zip code + city). Each column is assigned a certain data type, e.g. text, numeric, date or blob. The data can also be assigned properties, such as unique, contain check constraints, autoincrements, computed values, restricted to minimum and maximum values etc. etc.

Columns are defined under the Field Definition in the Create Table dialog or Table Editor, or their definition can be based on domains. They can, of course, also be defined directly in the SQL Editor. Each defined column has the following syntax:

 ColumnName <data_type>
 DEFAULT < Default value > | NULL | USER NOT NULL
 CONSTRAINT <constraint name> <constraint def>
 COLLATE <collation sequence>;

In a relational database the physical sequence of rows and columns is irrelevant.

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