Question

A field or a combination of fields that has a unique value is called :

Answer 1

A field or a combination of fields that has a unique value is called key or foreign key.

Answer 2

Answer:

A field or a combination of fields that has a unique value is called a candidate key.

Step-by-step explanation:

Candidate Key:

• A table represents a collection of records of various events. All of these records must be uniquely identified and separated, i.e., without duplication. By using keys, this hassle can be eliminated.

• Keys are attributes or sets of attributes that identify unique rows (or tuples) in tables (or relations). They are used to establish relationships between tables and columns in a relational database.

• A candidate key is an attribute that identifies a row uniquely within a table.

• Candidate keys are subsets of super key sets that contain no redundant attributes. Null values are also not allowed for candidate keys.

• Candidate and primary keys both serve the same purpose, which is to uniquely identify tuples, but they are also different from one another. For a table, we can have one or more candidate keys, but we can create only one primary key.

• Therefore, Candidate keys are fields or combinations of fields that have a unique value.

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