What is multivalued attribute? Multivalued attributes refer to attributes that can hold multiple values. Example : A customer has multiple phone numbers or an employee with various degrees. This creates the problem of normalization issues and data redundancy. Addressing these challenges is essential for maintaining data integrity and optimizing database performance.
Normalization Rules 1st Normal Form: Atomic, Avoid Repeating Groups, No Multivalued attributes, should have a primary key 2nd Normal Form: Should be in 1NF, Eliminate Partial Key Dependencies 3rd Normal Form: Should be in 2NF, Eliminate Transitive Dependencies First Normal Form Rules 1.Each column should contain atomic values. 2.Each set of related data should have…
Previous >>> Introduction to Normalization What is Functional Dependency? Functional dependencies are a fundamental concept in relational databases. They help ensure the accuracy and integrity of data by describing the relationships between different fields in database tables. If we have a set of attributes A and another set of attributes B, we can say that…
What is Normalization? Normalization is the process of assigning attributes to relations in such a way that data redundancies and Modification Abnormalities are reduced or eliminated. Problems in Unnormalized Database Data Redundancy Anomalies Data Redundancy Data redundancy in a database means that the same data is present in more than one table. Disadvantages Of…
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What are the Steps to Design an ER Diagram? Identify main entities in the scenario For each entity, identify the list of its attributes Identify the relationships between each entities Determine the cardinality of each relationship between entities Start drawing the entities and the relationships using rectangles and diamonds respectively Connect attributes to each entity…
Keys in Database are Primary Keys, Candidate key, Alternate key and Foreign Key. Candidate key A candidate key is a field or set of fields that could be used as the primary key. Like a primary key, it must be unique, but it is not necessarily chosen as the primary key. Primary Key A primary…
Foreign key is a field in a relational database table that establishes a relationship between two tables based on the values of one or more fields in each table. Foreign key Rule Foreign key in one table refers to the primary key in another table. The table containing the foreign key is called the referencing…
Mapping ER Diagrams to Database Schema is the second step in database design. Drawing ER diagram is the first step. Mapping a Composite attribute Mapping a Derived attribute Mapping a Multi valued attribute Mapping Descriptive attribute Mapping 1:1 Relationship Mapping 1:M Relationship Mapping M:N Relationship Mapping Weak Entity
Types of Relationships in ER Diagram One-to-One (1:1) One-to-Many (1:M) or Many-to-One (M:1) Many-to-Many (M:N) One-to-one (1:1) This is where an occurrence of an entity relates to just one occurrence in another entity. Example: An employee is allotted an organization vehicle, which is driven by that employee only. Therefore, there’s a one-to-one relationship between employee…