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Explain the concepts of relational data model?
Relational Data Model - The relational model was first introduced through Prof. E.F. Codd of the IBM Research in the year 1970 and attracted immediate attention because of its simplicity and mathematical foundation. The model uses the concept of a mathematical relation (such as a table of values) as its primary building block, and has its theoretical basis within set theory and first-order predicate logic. The relational model represents the database as a collection of relations. The relational model such as all other models consists of three basic elements:
The primary key is selected from the
why are older data models are being replaced by new data models
Replication : It is definite as a copy of a relation. Every replica is stored at a dissimilar site. The alternative to replication is to store only single copy of a relation which
What is a Built-in A notation of identity is built-into the data model or programming language and no user-supplied identifier is needed. This form of identity is used in objec
Aggregation Aggregation is stronger form of association. It represents the "has-a" or "part-of" relationship. An aggregation association depicts a complex object which is comp
Need for Multiple Access Paths In practice, most of the online information systems need the support of multi-key files. For example, consider a banking database application hav
Describe the types of Inheritance 1. Single inheritance 2. Multiple inheritance 3. Hierarchical inheritance 4. Multilevel inheritance
Explain ER Relationship model? An entity-relationship model (ERM): An entity-relationship model (ERM) is an abstract theoretical illustration of structured data. Entity-relatio
What is the use of unique function? UNIQUE function: If UNIQUE is specified then only unique values are used to computed the mean.
How to create a biological database based on viruses. How to decide which attribute should be there in the table and schema? How to identify the primary keys, foreign keys, domain,
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