June 2018
Intermediate to advanced
478 pages
10h 52m
English
Referential integrity constraints (also known as foreign key constraints or referential constraints) enable you to define required relationships between and within different tables. Referential integrity is the state of a database in which all values of all foreign keys are valid. A foreign key is a column or a set of columns in a table whose values are required to match at least one primary key or unique key value of a row in its parent table.
To understand how referential constraints work, let's establish a relationship between the EMPLOYEE and DEPARTMENT tables, as shown in the following diagram. In this example, a single column DEPTID defines the parent key and the foreign key of the referential constraint. ...