Important Notice: Our web hosting provider recently started charging us for additional visits, which was unexpected. In response, we're seeking donations. Depending on the situation, we may explore different monetization options for our Community and Expert Contributors. It's crucial to provide more returns for their expertise and offer more Expert Validated Answers or AI Validated Answers. Learn more about our hosting issue here.

What is a FOREIGN KEY constraint?

April 26, 2017column constraint foreign integrity key known referential specifies value

0

Posted

What is a FOREIGN KEY constraint?

1 Answer

0

Posted

A FOREIGN KEY constraint (also known as referential integrity constraint) specifies that each value in a specified column or set of columns must match a value in another table’s unique or primary key (column or set of columns protected by a UNIQUE or PRIMARY KEY constraint). A column or set of columns protected by a FOREIGN KEY constraint is known as a foreign key. A table having a foreign key is called child table. A table having a unique or primary key referenced by a foreign key is called parent table. A table’s foreign key can reference to the same table’s unique or primary key. A foreign key can contain duplicate and NULL values.