Is foreign key dependent on primary key?

For example, the foreign key must reference a primary key or unique constraint, although that reference can be on the same table or on a different table.

What is the relationship between primary and foreign key?

A foreign key is a column or a set of columns in one table that references the primary key columns in another table. The primary key is defined as a column (or set of columns) where each value is unique and identifies a single row of the table.

Can a foreign key be part of a primary key?

This is not possible. The foreign key can not refer to part of composite primary key of other table. Because it is supposed to be one-to-one relationship and if you refer just part of primary-key, there might be more than one parent record available, which is neither allowed nor possible.

Can a foreign key be a primary key in the same table?

If you mean “can foreign key ‘refer’ to a primary key in the same table?”, the answer is a firm yes as some replied.

Can we use foreign key without 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.

Can primary key and foreign key be in the same table?

What are foreign keys used for?

Foreign keys link data in one table to the data in another table. A foreign key column in a table points to a column with unique values in another table (often the primary key column) to create a way of cross-referencing the two tables.

Can a foreign key exist without primary key?

A FOREIGN KEY constraint does not have to be linked only to a PRIMARY KEY constraint in another table; it can also be defined to reference the columns of a UNIQUE constraint in another table. So in your case if you make AnotherID unique, it will be allowed.

Can a foreign key be a non primary key?

A foreign key can refer to either a unique or a primary key of the parent table. If the foreign key refers to a non-primary unique key, you must specify the column names of the key explicitly.