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Why do you designate one of the candidate key of relation to be the primary key?
We designate one of the candidate key of a relation to be a primary key because that primary key is use for any foreign key references.
What is candidate key in dbms?
more than one primary key to identify the record uniquely is called candidate key.
How do foreign keys ofrelations relate to candidate keys?
Foreign keys and candidate keys serve distinct roles in relational databases. A candidate key is a set of one or more attributes that can uniquely identify a tuple within a relation, while a foreign key is an attribute or a set of attributes in one relation that refers to the primary key of another relation. Foreign keys establish relationships between tables, ensuring referential integrity, whereas candidate keys ensure that each row within a table can be uniquely identified. Thus, while foreign keys link tables, candidate keys define uniqueness within a table.
Candidate key and primary key differnece?
All Primary keys are definitely Candidate Keys. A Candidate key is one which can be used as a Primary key that is not null and unique. That is one of the candidate keys can be chosen as a primary key.A Candidate key is a Unique Key and it can be used to find out any particular Tuple (row) in a table. The following are the differences between A Candidate key and a Primary Key: 1) A Unique key can be null but not a Primary key 2) On a table we can have only 1 primary key but 'N' number of unique keys.
Why do we designate one of the candidate keys of a relation to be the primary key?
A primary key is designated from among the candidate keys of a relation to uniquely identify each record in that relation and to ensure data integrity. It serves as a reference point for establishing relationships with other tables, facilitating efficient data retrieval and manipulation. Additionally, the primary key typically has constraints that prevent null values and duplicates, reinforcing the uniqueness of each entry in the database.
Explain two rules in relational model of database systems?
1) Entity Integrity: In a base relation, no attribute of a primary key can be null. 2) Referential Integrity: If foreign key exists in a relation, either foreign key value must match a candidate key value of some tuple in its home relation or foreign key value must be wholly null
What ievery determinant is candidate key?
A candidate key is a minimal set of attributes in a relational database that can uniquely identify a tuple (row) in a table. Every determinant, which is an attribute or a set of attributes that can determine another attribute, can be a candidate key if it uniquely identifies all other attributes in the relation and is minimal. This means that if any attribute is removed from the determinant, it no longer uniquely identifies the tuples. In essence, every candidate key is a determinant, but not all determinants qualify as candidate keys.
What is difference between primary candidate and candidate key?
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Why do we designate one of the candidate keys of a relation be the primary key?
A primary key is designated from one of the candidate keys to uniquely identify each record in a relation, ensuring data integrity and preventing duplicate entries. It serves as a reference point for establishing relationships between tables in a database. Additionally, the primary key is typically optimized for performance, as it is often indexed, facilitating efficient data retrieval. Choosing a primary key also simplifies database design and enhances clarity in data management.
Difference between a super key and a candidate key?
Different set of attributes which are able to identify any row in the database is known as super key. And minimal super key is termed as candidate key i.e. among set of super keys one with minimum number of attributes. Primary key could be any key which is able to identify a specific row in database in a unique manner.
What is the difference between primary key and candidate key?
Candidate Key is used to uniquely identify the records of a table. An attribute becomes a Primary Key, if all the other candidate keys lose race for being qualified as Primary Key.
What conditions are required for 3NF violation to occur?
A relation violates third normal form (3NF) if it has a transitive dependency where a non-prime attribute depends on another non-prime attribute (which itself is not a candidate key). This means that a non-prime attribute is functionally dependent on another non-prime attribute rather than on a candidate key.
