Uses of the term Database table
The term table
takes on a dual meaning when we talk about database design. On the one hand, the elements comprising an ER diagram are referred to as base tables.
These are represented as
- entities and
- attributes, which represent the business objects
to be included in the database, and are the sort of tables during the process of relational database design.
They come into play during the Logical Design phase of the (DBLC) database lifye cycle.
We also use the term table to refer to the relational constructs comprising the implementation of the database.
These tables will be described in greater detail later in this module.
A table is a collection of related data held in a structured format within a database. It consists of fields (columns), and rows.
In relational databases, a table is a set of data elements using a model of vertical columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect.
A table has a specified number of columns, but can have any number of rows. Each row is identified by one or more values appearing in a particular column subset. The columns subset which uniquely identifies a row is called the primary key.
Table is another term for "relation", although there is a difference in that a table is usually a combination of rows where a relation is a set and does not allow duplicates. Besides the actual data rows, tables generally have associated with them metadata, such as constraints on the table or on the values within particular columns.
The data in a table does not have to be physically stored in the database. Views also function as relational tables, however their data are calculated when a query is executed.