What is the difference between the primary key and foreign key?
What is the difference between the primary key and foreign key?
A primary key is used to ensure data in the specific column is unique. A foreign key is a column or group of columns in a relational database table that provides a link between data in two tables. It uniquely identifies a record in the relational database table.
Can two tables have the same primary key?
Yes. You can have same column name as primary key in multiple tables. Column names should be unique within a table. A table can have only one primary key, as it defines the Entity integrity.
What is the difference between primary key and foreign key?
On the other hand, foreign key is used to maintain relationship between two tables. Primary of a table act as forgein key in the other table. Foreign key in a table enforce Referential Integrity constraint. It can be more than one in the table.
How many primary and foreign keys are allowed in a table?
Only one primary key is allowed in a table. Whereas more than one foreign key are allowed in a table. It is a combination of UNIQUE and Not Null constraints. It can contain duplicate values and a table in a relational database. It does not allow NULL values.
What is the difference between primary key and foreign key in RDBMS?
But the Foreign Key of a table in RDBMS can contain Null values. A Primary Key is specified while defining the table, and it is compulsory to define the Primary Key. Unlike the Primary Key, there is no specific table definition for denoting a Key to be Foreign Key.
What is the use of foreign key in database?
Foreign keys help you to migrate entities using a primary key from the parent table. A foreign key enables you to link two or more tables together. It makes your database data consistent. A foreign key can be used to match a column or combination of columns with primary key in a parent table.
