What is difference between candidate key and unique key?
Candidate key is a set of columns which can uniquely identify the values in a table and can act as a unique key. Unique key as the name suggests , is used to uniquely identify a value in a table. For example Emp_id etc. Every candidate key will act as a unique key.
Is candidate key always primary key?
Each Candidate Key can qualify as Primary Key. Primary Key – A Primary Key is a column or a combination of columns that uniquely identify a record. Only one Candidate Key can be Primary Key.
What is the difference between a candidate key and the primary key for a given relation What is a Superkey?
1. Super Key is an attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation. Primary Key is a minimal set of attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation. We can choose any of the minimal candidate key to be a primary key.
What is a candidate key example?
Candidate Key: The minimal set of attributes that can uniquely identify a tuple is known as a candidate key. For Example, STUD_NO in STUDENT relation. For Example, STUD_NO is the candidate key for relation STUDENT. The candidate key can be simple (having only one attribute) or composite as well.
What is the meaning of candidate key in database?
A candidate key is a specific type of field in a relational database that can identify each unique record independently of any other data. Experts describe a candidate key of having “no redundant attributes” and being a “minimal representation of a tuple” in a relational database table.
What is meant by candidate key?
What is candidate key explain with example?
Candidate Key: The minimal set of attributes that can uniquely identify a tuple is known as a candidate key. For Example, STUD_NO in STUDENT relation. The value of the Candidate Key is unique and non-null for every tuple. For Example, STUD_NO is the candidate key for relation STUDENT.
Why all super keys are not candidate keys?
Super Key is an attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation. Candidate Key is a subset of a super key. In a relation, number of super keys are more than number of candidate keys. While in a relation, number of candidate keys are less than number of super keys.
What does FK mean in database?
foreign key
A foreign key (FK) is a column or combination of columns that is used to establish and enforce a link between the data in two tables to control the data that can be stored in the foreign key table.