What is difference between candidate key and primary key?

Primary Key is a unique and non-null key which identify a record uniquely in table. A table can have only one primary key. Candidate key is also a unique key to identify a record uniquely in a table but a table can have multiple candidate keys.

What are the differences between primary foreign and unique keys?

S.NO. 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.

What is super key and foreign key?

Super Key – A super key is a set of one of more columns (attributes) to uniquely identify rows in a table. Foreign Key – Foreign keys are the columns of a table that points to the primary key of another table. They act as a cross-reference between tables.

Is primary key candidate key?

Primary key is a Candidate key chosen to uniquely identify tuples in the table. Primary key values should be unique and non-null. There can be multiple Super keys and Candidate keys in a table, but there can be only one Primary key in a table.

What’s the difference between a candidate key and a foreign key?

Primary key – The candidate key chosen to identify tuples uniquely within the relation. Alternate key – Candidate key that is not a primary key. Foreign key – An attribute or set of attributes within a relation that matches the candidate key of some relation. Attribute or set of attributes used to uniquely identify tuples in the database.

What’s the difference between a Super key and a foreign key?

Foreign key – An attribute or set of attributes within a relation that matches the candidate key of some relation. Attribute or set of attributes used to uniquely identify tuples in the database. Super Key : Super key is a set of one or more attributes whose values identify tuple in the relation uniquely.

What’s the difference between Super key and candidate key?

1. Super Key: Super Key is an attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation. All super keys can’t be candidate keys but its reverse is true. In a relation, number of super keys are more than number of candidate keys.

Can a Super key be an alternate key?

There can be multiple Super keys and Candidate keys in a table, but there can be only one Primary key in a table. Alternate keys are those Candidate keys that were not chosen to be the Primary key of the table. Composite key is a Candidate key that consists of more than one attribute.