Question

Which of the following is correct syntax for inserting foreign key constraint in a relation?

• A. ALTER TABLE table_name ADD FOREIGN KEY(attribute_name) REFERENCES referenced_table_name(attribute_name)
• B. ADD TABLE table_name ADD FOREIGN KEY(attribute_name) REFERENCES referenced_table_name(attribute_name)
• C. ALTER TABLE table_name REFERENCES referenced_table_name(attribute_name) ADD FOREIGN KEY(attribute_name)
• D. MODIFY TABLE table_name ADD FOREIGN KEY(attribute_name) REFERENCES referenced_table_name(attribute_name)

Answer 1

The Correct Option is A

To establish a foreign key constraint in a relation, the syntax is: ALTER TABLE table_name ADD FOREIGN KEY(attribute_name) REFERENCES referenced_table_name(attribute_name). The ALTER TABLE statement modifies an existing table. The ADD FOREIGN KEY clause designates a column to link to a primary key in another table. The components of this syntax are:

• ALTER TABLE table_name: Designates the table to be modified.
• ADD FOREIGN KEY(attribute_name): Specifies the addition of a foreign key constraint to the designated column, attribute_name, in the current table.
• REFERENCES referenced_table_name(attribute_name): Identifies the target table, referenced_table_name, and the specific column within that table, attribute_name, to which the foreign key will point.

Correct application of this syntax enforces referential integrity, ensuring consistent data relationships across tables.