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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 data dependency in DBMS?
Data dependency in DBMS refers to the relationship between different data elements within a database. There are three main types: functional dependency (one attribute determines another), partial dependency (part of a composite key determines other attributes), and transitive dependency (dependency between non-key attributes). Understanding data dependencies is crucial for database normalization and maintaining data integrity.
Discuss the difference between a composite key and a composite attribute.How would each be indicated in an ERD?
Attribute is the property of entity.The composite attribute is like address(where street no,house no,town name all include).Composite key is also an attribute,but only which attribute are work as a unique identifier. Example:> In an ERD if vendor placed with orders then order(order day, order number) vendor(vendor code,vendor address) Here, order and vendor both are entity and order number, vendor code both are Composite key(because those are unique)but vendor address is a Composite attribute and order day(may be not unique)is an attribute only. So, we can conclude that all attribute not Composite key.
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.
Is a unique identifier also called a record key?
The normal term would be a primary key, not a record key.
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).
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 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.
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 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
How is concept of functional dependency associate with process of normalization?
Functional dependency is a key concept in database normalization, as it defines the relationship between attributes in a relation. It indicates that the value of one attribute (or a group of attributes) uniquely determines the value of another attribute. Normalization utilizes these dependencies to organize data efficiently, eliminating redundancy and minimizing the potential for update anomalies. By identifying and enforcing functional dependencies, databases can be structured in a way that enhances data integrity and reduces duplication.
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 data dependency in DBMS?
Data dependency in DBMS refers to the relationship between different data elements within a database. There are three main types: functional dependency (one attribute determines another), partial dependency (part of a composite key determines other attributes), and transitive dependency (dependency between non-key attributes). Understanding data dependencies is crucial for database normalization and maintaining data integrity.
What is the prime attribute in a database?
It is an attribute that does not occur in some candidate key.
