Database System & Designs

determinations

the state in which knowing the value of one attribute makes it possible to determine the value of another

dependence

a relationship between different attributes in a table, where the value of one attribute is determined by the value of another attribute.

functional dependence

the value of one or more attributes determines the value of one or more attributes

determinant

any attribute in a specific row whose value directly determines other values in that row

dependent

an attribute (or set of attributes) whose value depends on another attribute or set of attributes. The dependent attribute's value is determined or constrained by the value of another attribute(s) in the same relation (table).

primary key

a field in a table that uniquely identifies each record in that table. Every table in a relational database should have a primary key to ensure that each record is distinct and can be efficiently accessed.

super key

a set of one or more attributes (columns) that can uniquely identify each record in a table. In other words, any combination of attributes that can uniquely identify every row in the table, though it may contain extra, unnecessary attributes.

candidate key

a minimal set of attributes (columns) that can uniquely identify each record in a table. It is a superkey with no unnecessary or redundant attributes.

foreign key

an attribute (or a set of attributes) in a table that creates a link between the data in two tables.

secondary key

an attribute (or a set of attributes) that is used to access records in a table, but it is not the primary key. It is an alternate way of accessing or retrieving records, and typically, it is used for querying and searching purposes.

why is it important to identify dependents?

To avoid redundancy and ensure efficient data storage, you break up tables based on their dependencies.

what is a foreign key used for?

to enforce referential integrity by ensuring that the value in the foreign key column(s) matches a valid value in the referenced table's primary key or another unique key.