foreign key उदाहरण वाक्य

उदाहरण वाक्य

1. "Foreign keys " are integrity constraints enforcing that the operation that draws on information from several relations at once.
2. The Foreign Key serves as the link, and therefore the connection, between the two related tables in this sample database.
3. Typically the field being used as the link, the " foreign key ", will be indexed for quick lookup.
4. For instance, deleting a record that contains a value referred to by a foreign key in another table would break referential integrity.
5. This means that any one, none, or all, of the multiple attributes within the compound key can be foreign keys.
6. Foreign keys may be the primary key in another table; for example a PersonID may become the EmployeeID in the Employee table.
7. Both foreign keys and superkeys ( that includes candidate keys ) can be composite, that is, can be composed of several attributes.
8. In other words, when a foreign key value is used it must reference a valid, existing primary key in the parent table.
9. The adjective'referential'describes the action that a foreign key performs,'referring'to a link column in another table.
10. In simpler words, the foreign key is defined in a second table, but it refers to the primary key in the first table.