How is foreign key commands different from primary key command?

A primary key uniquely identifies a record in the relational database table, whereas a foreign key refers to the field in a table which is the primary key of another table.

Does a primary key have to be linked to a foreign key?

From Books Online: 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.

Can primary key also be foreign 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. Yes, it is legal to have a primary key being a foreign key.

Can primary key and foreign key have same name?

To facilitate keeping key variable names consistent, and to provide for programs that do natural joins, foreign keys have the same name as is used in the table in which they are the primary key.

Is a foreign key a primary key in another table?

A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the PRIMARY KEY in another table. The table with the foreign key is called the child table, and the table with the primary key is called the referenced or parent table.

Can foreign key also be primary key?

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 be the foreign key at the same time?

These are totally different constructs. A Primary Key is used to enforce uniqueness within a table, and be a unique identifier for a certain record. A Foreign Key is used for referential integrity, to make sure that a value exists in another table. The Foreign key needs to reference the primary key in another table.

Are primary key and foreign key the same?

A primary key is a column or a set of columns in a table whose values uniquely identify a row in the table. A foreign key is a column or a set of columns in a table whose values correspond to the values of the primary key in another table.

Can we have primary key and foreign key in same column?

Basically foreign key is primary key of the related table. So you cannot have the same column with primary key and foreign key.

How does foreign key work?

A Foreign Key is a database key that is used to link two tables together. The FOREIGN KEY constraint identifies the relationships between the database tables by referencing a column, or set of columns, in the Child table that contains the foreign key, to the PRIMARY KEY column or set of columns, in the Parent table.

How do I create a foreign key?

To create a Foreign Key using the SSMS GUI, using Object Explorer select the referencing table dbo.Product, go to Keys, right click on Keys and select New Foreign Key…: The table designer will open as well as a new window like below. Click on the ellipse (…) next to Tables and Columns Specification.

What is the difference between foreign key and primary key?

The difference between foreign key and primary key is that foreign key is a column or a set of columns that refer to a primary key or a candidate key of another table while primary key is a column or a set of columns that can be used to uniquely identify a row in a table.

How do I create a primary key?

To create a primary key In Table Designer, click the row selector for the database column you want to define as the primary key. If you want to select multiple columns, hold down the CTRL key while you click the row selectors for the other columns. Right-click the row selector for the column and select Set Primary Key.

What is primary foreign key relationship?

A primary key-foreign key relationship defines a one-to-many relationship between two tables in a relational database. A foreign key is a column or a set of columns in one table that references the primary key columns in another table.