IST359 - Relational Database Model

table

A primary unit of storage in the relational model, a 2D structure consisting of rows and columns.

relation

A table with a column (or set of columns) for which the data in those columns can be used to find one unique row.

column

Represents a category of data in a relational table. For example in a table of customers, this would be the customer phone number.

row

Represents an instance of data in a relational table. For example in a table of students this might be YOU.

attribute

Represents one atomic member of a table at the intersection of a row and a column.

physical domain

The acceptable data type for a column in a table.

logical domain

The set of values which are acceptable for a column in a table.

constraint

A rule or condition which restricts allowable data in either a table or a column.

default value

A constraint where specific data is used when one is not specified.

check constraint

A condition which must be "true" prior to data being added or changed.

Unique constraint

A condition which forbids duplicate values in a column or group of columns.

primary key

A constraint on a column or group of columns which uniquely identifies each row in a table.

foreign key

A constraint on a column or set of columns which ensure is values come from another table's primary key values.

surrogate key

An auto-generated value, typically used as primary key.

candidate key

Any column or set of columns which could function as a primary key

null

A special value which means "the absence of a value" or "no value."

entity integrity

Each row in a table must be uniquely identifiable. Any table with a primary key constraint has this characteristic.

referential integrity

The column must either contain null or a value which is a primary key in another table. Any table with a foreign key constraint has this characteristic.