4.9

Plural Attributes

Attributes that can have multiple values, necessitating the creation of a new weak table with a foreign key referencing the initial table.

Weak Table

A table that holds attributes that depend on another table, where composite keys are used to uniquely identify its rows.

Foreign Key

A column that creates a relationship between two tables, referencing the primary key of another table.

Primary Key Cascade

A rule that automatically deletes or updates rows in child tables when the corresponding rows in the parent table are deleted or updated.

Foreign Key Restrict

A rule that prevents the deletion or updating of rows in a parent table if there are corresponding rows in a child table.

Data Type

The format or type of data that can be stored in a given column, determined by the attribute type.

Required Entity

An entity that must have a corresponding record in another table, which makes the foreign key column required.

Singular Entity Unique Column

A column that is unique within a table, enforcing that no two rows have the same value in this column.

NOT NULL

A constraint that specifies that a column cannot have a NULL value, ensuring data integrity.

UNIQUE Constraint

A constraint that ensures all values in a column are different from each other.