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Explain ER Relationship model?
An entity-relationship model (ERM): An entity-relationship model (ERM) is an abstract theoretical illustration of structured data. Entity-relationship modelling is a relational schema database modelling techniques, used in software engineering to produce a kind of conceptual data model (or semantic data model) of a system, frequent a relational database, and its needs in a top-down fashion. Diagrams created using this procedure are known as entity-relationship diagrams, or ER diagrams or ERDs for short.
Benefits: It limits data access. It makes difficult queries look easy. It permits data independence. It presents dissimilar views of the similar data.
What is a SELECT operation? The select operation selects tuples that please a given predicate. We use the lowercase letter σ to denote selection.
define lock conversion
Explain the Log Based Recovery Method? The system log that is generally written on stable storage consists of the redundant data required to recover from volatile storage failu
Cardinality shows the number of instances of an entity associated with another entity participating in a relationship. Depend on the cardinality binary relationship can be further
Q. Explain data aggregatio n and discuss different design constraints. Sol. Aggregation One limitation of the E-R model is that it cannot express relationships amon
notes about update opreation
Strong entity set and weak entity set? Strong entity set and weak entity set: A strong entity set has a primary key. All tuples in the set are distinguishable through that key.
Explain the concept of a data model ? Data Model - Model is an abstraction procedure which hides irrelevant details although highlighting details relevant to the application
Single-Valued Dependencies A database is a collection of related information and it is therefore inevitable that some items of information in the database would depend on some
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