What is a foreign key easy definition?

What is a foreign key easy definition?

A foreign key is a column (or combination of columns) in a table whose values must match values of a column in some other table. FOREIGN KEY constraints enforce referential integrity, which essentially says that if column value A refers to column value B, then column value B must exist.

What is the correct definition of foreign key?

A foreign key is defined as an attribute or set of attributes in a relation whose values match a primary key in another relation. The syntax to add such a constraint to an existing table is defined in SQL:2003 as shown below.

What is the importance of foreign key?

The primary purpose of the foreign key constraint is to enforce referential integrity and improve performance, but there are additional benefits of including them in your database design.

Which is the best definition of a foreign key?

Definition – What does Foreign Key mean? A foreign key is a column or group of columns in a relational database table that provides a link between data in two tables. It acts as a cross-reference between tables because it references the primary key of another table, thereby establishing a link between them.

What is the purpose of an oracle foreign key?

What is Oracle FOREIGN Key? An Oracle FOREIGN Key is used to define an integrity constraint that restricts the values in a Database Table. The table which contains a FOREIGN key called the child table. The FOREIGN key column data reference the parent column data.

How is a foreign key related to a child table?

This referential link helps to match the foreign key column data with the data of the referenced table data. The referenced table is called the parent table and the table that involves a foreign key is called the child table. In addition, if a foreign key references another column of the same table, this reference type is called a self-reference.

When do you use the FOREIGN KEY constraint?

The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables. A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the PRIMARY KEY in another table.