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Can both primary and foreign key be?
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 you have more than one foreign key?
A table may have multiple foreign keys, and each foreign key can have a different parent table. Each foreign key is enforced independently by the database system.
What is the difference between primary 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. Only one primary key is allowed in a table.
What is relationship between a primary and a foreign key?
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. A primary key must be unique and only one primary key is allowed in a table which must be defined, whereas more than one foreign key are allowed in a table.
What is difference between primary key and foreign key?
What is the Difference Between Primary Key and Foreign Key. The main difference between primary key and foreign key is that the primary key is used to identify the records in the table uniquely while the foreign key is used to connect two table together. Most business organizations use databases to store data.
What is difference between “primary key” and “unique key”?
Primary key can be considered as a special case of the unique key. Another difference is that primary keys have an implicit NOT NULL constraint while the unique key does not have that constraint. Therefore, unique key columns may or may not contain NULL values but primary key columns cannot contain NULL values.
What is the difference between primary key and candidate key?
The main difference between primary key and candidate key is that primary key is the minimal set of attributes of the table that helps to identify each row uniquely, while candidate key is a super key with no redundant attributes. Generally, a database of an RDBMS consists of multiple tables.