Relational Model conceptThe relational model can represent as a table with columns and rows. Each row is known as a tuple. Each table of the column has a name or attribute.Domain: It contains a set of atomic values that an attribute can take.Attribute: It contains the name of a column in a particular table. Each attribute Ai must have...
04 April, 2022
Relationship of higher degree
Relationship of higher degreeThe degree of relationship can be defined as the number of occurrences in one entity that is associated with the number of occurrences in another entity.There are the three degrees of relationship:One-to-one (1:1)One-to-many...
Reduction of ER diagram to Table
Reduction of ER diagram to TableThe database can be represented using the notations, and these notations can be reduced to a collection of tables.In the database, every entity set or relationship set can be represented in tabular form.The ER...
Aggregation
AggregationIn aggregation, the relation between two entities is treated as a single entity. In aggregation, the higher-level relationship with its corresponding entities is aggregated into a higher-level entity.For example, the Center...
Specialization
SpecializationSpecialization is a top-down approach, and it is opposite to Generalization. In specialization, one higher level entity can be broken down into two lower level entities.Specialization is used to identify the subset of an...
Generalization
GeneralizationGeneralization is like a bottom-up approach in which two or more entities of lower-level levels combine to form a higher-level entity if they have some attributes in common.In generalization, an entity of a higher level can also...
DBMS Keys
KeysKeys play an important role in the relational database.It is used to uniquely identify any record or row of data from the table. It is also used to establish and identify relationships between tables.For example, ID is used as a key...
Mapping Constraints
Mapping ConstraintsA mapping constraint is a data constraint that expresses the number of entities to which another entity can be related via a relationship set.It is most useful in describing the relationship sets that involve more than...
ER Design Issues
ER Design IssuesIn the previous sections of the data modeling, we learned to design an ER diagram. We also discussed different ways of defining entity sets and relationships among them. We also understood the various designing shapes that represent a relationship, an entity, and its attributes. However, users often mislead the concept of the...
DBMS Notation of ER diagram
Notation of ER diagramDatabase can be represented using the notations. In ER diagram, many notations are used to express the cardinality. These notations are as follows:Fig: Notations of ER diag...
DBMS ER Model Concept
ER modelER model stands for an Entity-Relationship model. It is a high-level data model. This model is used to define the data elements and relationship for a specified system.It develops a conceptual design for the database. It also develops...