referential integrity-
referential integrity means which primary/foreign key relationships are enforced in a database. By specifying the referential integrity rules you can have the database guarantee, an example of this would be that every sales representative is assigned to a valid office. Through the use of referential integrity constraints, many business rules can be enforced by the database server, instead of your application.
The terms "primary key" and "foreign key" are used throughout these documents.
Primary Key- A unique identifier for a table. A column or column combination with the property that, at any given time, no two rows of the table contain the same value in that column or column combination. this would be your name, age and gender etc...
Foreign Key- A foreign key is a column or combination of columns whose values match the primary key of some other table. A foreign key does not have to be unique; in fact, foreign keys are often in a many-to-one relationship to a primary key. Foreign key values should be copies of the primary key values; no value in the foreign key except NULL should ever exist unless the same value exists in the primary key. A foreign key may be NULL; if any part of a composite foreign key is NULL, the entire foreign key is NULL.
