Can you have multiple foreign keys from the same table?

A table may have multiple foreign keys, and each foreign key can have a different parent table. Each foreign key is enforced independently by the database system.

What is not true about foreign key?

Question 22 options: A foreign key is a duplicated column from a related table A foreign key must be unique A foreign key is a referential integrity constrain t A foreign key establishes a relationship with a primary key in a related table.

Which statement is false for a foreign key constraint?

FOREIGN KEY constraints are not enforced on temporary tables. FOREIGN KEY constraints cannot reference another column in the same table.

Should a foreign key be unique?

By the SQL standard, a foreign key must reference either the primary key or a unique key of the parent table. If the primary key has multiple columns, the foreign key must have the same number and order of columns. Therefore the foreign key references a unique row in the parent table; there can be no duplicates.

Why are foreign key constraints used?

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.

What is a foreign key constraint Why are such constraints important what is referential integrity?

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.

Which of the following foreign key constraint specifies that the deletion fails with an error?

8. Which of the following foreign key constraint specifies that the deletion fails with an error? Explanation: The ON UPDATE clause defines the actions that are taken if you try to update a candidate key value to which existing foreign keys point.

Does a foreign key always reference a primary key?

A foreign key must refer to an entire primary key, and not just part of it. Consider a Department table with a primary key of company_name + department_name. An Employee table should only refer to both attributes and not to department_name alone.

Should foreign key always be a primary key?

Primary keys always need to be unique, foreign keys need to allow non-unique values if the table is a one-to-many relationship. It is perfectly fine to use a foreign key as the primary key if the table is connected by a one-to-one relationship, not a one-to-many relationship.