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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.
What else can I help you with?
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.
How do you Avoid missing column values for non primary key columns?
Use Default and Not NULL
What is the strongest number?
Strength is not an attribute of numbers.
What is a simple attribute in dbms?
database simple attritbute
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.
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 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 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 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
foreign key?
when a primary key from one table is stored as an attribute of another table
Why is a Key important in a database?
a key is important in a database because using of that key only we can identify a unique attribute.
What is non transitive dependency?
Non-transitive dependency occurs in a database when a relationship between three or more attributes does not imply a direct relationship between all of them. Specifically, if attribute A is dependent on attribute B, and attribute B is dependent on attribute C, it does not necessarily mean that attribute A is dependent on attribute C. This type of dependency can complicate database normalization and design, as it can lead to redundancy and anomalies in data management. Understanding non-transitive dependencies is crucial for ensuring data integrity in relational databases.
