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Attributes can be classified as identifiers or descriptors. Identifiers, more commonly called keys or key attributes uniquely identify an instance of an entity. If such an attribute doesn't exist naturally, a new attribute is defined for that purpose, for example an ID number or code. A descriptor describes a non-unique characteristic of an entity instance.
An entity usually has an attribute whose values are distinct for each individual entity. This attribute uniquely identifies the individual entity. Such an attribute is called a key attribute. For example, in the Employee entity type, EmpNo is the key attribute since no two employees can have same employee number. Similarly, for Product entity type, ProdId is the key attribute.
There may be a case when one single attribute is not sufficient to identify entities. Then a combination of attributes can solve this purpose. We can form a group of more than one attribute and use this combination as a key attribute. That is known as a composite key attribute. When identifying attributes of entities, identifying key attribute is very important.
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What is key attribute and non key attribute?
A key attribute is a characteristic of an entity that uniquely identifies each instance of that entity in a database, such as a primary key in a table. For example, in a customer database, a customer ID serves as a key attribute. In contrast, a non-key attribute provides additional information about the entity but does not uniquely identify it; for instance, a customer's name or email address would be considered non-key attributes. Together, key and non-key attributes help structure and define the data within a database.
Do non integral prime numbers exist?
No. The attribute "prime" and "composite" applies only to integers.
What is a simple key in database?
A simple key consists of a single attribute to uniquely identify an entity occurrence, for example, a student number, which uniquely identifies a particular student. No two students would have the same student number.
A relation that contains minimal redundancy and allows easy use is considered to be?
A relation that contains minimal redundancy and allows for easy use is considered to be in Third Normal Form (3NF). This normalization form eliminates transitive dependencies and ensures that every non-key attribute is fully functionally dependent on the primary key. By achieving 3NF, the database design promotes data integrity and reduces the likelihood of anomalies during data manipulation.
How do you Avoid missing column values for non primary key columns?
Use Default and Not NULL
Non-prime attribute in DBMS?
Prime attribute are part of any candidate key. Non-prime attribute are not part of any candidate key.
What is key attribute and non key attributes?
A key attribute is an attribute that uniquely identifies a record in a database table. Non-key attributes are attributes that are not used to uniquely identify records, but provide additional information about the data.
What is key attribute and non key attribute?
A key attribute is a characteristic of an entity that uniquely identifies each instance of that entity in a database, such as a primary key in a table. For example, in a customer database, a customer ID serves as a key attribute. In contrast, a non-key attribute provides additional information about the entity but does not uniquely identify it; for instance, a customer's name or email address would be considered non-key attributes. Together, key and non-key attributes help structure and define the data within a database.
Is foreign key a non key attribute?
a key to a different table
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.
What is a non key attribute in normalization?
An attribute is another name for a field in a table. Some attributes are used as keys to help specifically identify individual records,like a code number or reference number for example. Most attributes are not used as keys. Any of those are non-key attributes.
What are the requirements for a relation to be in Second Normal Form?
A relation is in second normal form (2NF) if any of the following conditions apply: The primary key consists of only one attribute No non-primary key attribute exists in the relation Every non-primary key attribute is functionally dependent on the full set of primary key attributes
What is transitive dependency in normalization?
Transitive dependency in database normalization refers to a situation where a non-key attribute depends on another non-key attribute rather than directly depending on the primary key. This can lead to redundancy and anomalies during data manipulation. To eliminate transitive dependencies, a database is typically decomposed into multiple tables, ensuring that each non-key attribute is functionally dependent only on the primary key. This is a key consideration when moving a database schema into Third Normal Form (3NF).
What condition are required for 2NF violation to occur?
A table violates Second Normal Form (2NF) if it is not in First Normal Form (1NF) and has partial dependencies. This means that a non-prime attribute (an attribute that is not part of any candidate key) depends only on a subset of a composite primary key, rather than on the whole key. To achieve 2NF, each non-prime attribute must be fully functionally dependent on the entire primary key.
What is the prime attribute in a database?
It is an attribute that does not occur in some candidate key.
A condition in which one attribute is dependent on another attribute when neither attribute is part of the primary key?
transitive dependency
How would you describe a condition in which one attribute is dependent on another attribute when neither attribute is part of the primary key?
Transitive Dependency
