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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.
foreign key?
when a primary key from one table is stored as an attribute of another table
Explain the concept of foreign key How a foreign key differs from a primary key?
Foreign keys are used to link one database with another. A primary key is an attribute of a record that allows users to identify information.
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 key attribute and non key attribute?
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 is Foreign key plus attribute is know as?
A foreign key combined with attributes is known as a "composite key" when it includes more than one attribute. However, if the foreign key itself is being described in relation to its attributes, it typically refers to the relationship between tables where the foreign key in one table points to the primary key of another table, establishing a link between the two. This linkage helps maintain referential integrity within the database.
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 difference between primary key and foreign key?
A primary key is an attribute (or combination of attributes) that uniquely identifies each row in a relation. A primary key is designated by underlining the attribute name. The primary key of an entity set allows us to distinguish among the various entities of the set. A foreign key is an attribute in a relation of database that serves as the primary key of another relation in the same database.
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.
