What is the difference between a primary key and a foreign key?
The primary key is a unique identifier within its table, whereas a foreign key is a reference in one table to a primary key in another. Primary keys enforce uniqueness within their table, ensuring each record is identifiable. Foreign keys, however, are used to establish and navigate relationships between tables.
How can a primary key be used as a foreign key?
In a foreign key reference, a link is created between two tables when the column or columns that hold the primary key value for one table are referenced by the column or columns in another table. This column becomes a foreign key in the second table.
Can there be a foreign key without a primary key?
A foreign key is one or more columns in a table that references the primary key of another, creating a link between them. Foreign keys cannot exist without being linked to a primary key. Unlike primary keys, tables can have more than one foreign key.
Can a key be both a primary and foreign key?
Yes, it's possible.
Primary Key: It’s a special number that makes sure each item (or in our example, each car) is unique. · Foreign Key: It’s a number that points to …
Primary keys are simpler to define; Foreign keys require specifying the reference table and column; Foreign keys can have additional options (ON …
Foreign Key: Is the Primary Key one table appearing (cross-referenced) in another table. Secondary (or Alternative) Key: Is any field in the …