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Explain view in RDBMS?
View - A view is a relation (virtual rather than base) and could be used in query expressions, which is, queries can be written by using the view as a relation. Instead, a view is a named table in which is represented, not through its own physically separate stored data, but through its definition in terms of other named tables (base tables or views). The base relations on that a view is based are sometimes known as the existing relations. The definition of a view in a create view statement is stored within the system catalog. The syntax to create a view is:
CREATE [OR REPLACE] VIEW [()] AS
WITH {READ ONLY|CHECK OPTION [CONSTRAINT
]};
Dependency Preservation It is obvious that the decomposition must be lossless so that we do not lose any information from the relation that is decomposed. Dependency preservati
What is called an evaluation primitive? A relational algebra operation annotated with instructions on how to evaluate is known as an evaluation primitive.
Explain the term - Control as Concurrent Tasks As we know, any object can be implemented as a task in programming language or operating system. This is the most general approa
Question 1 Create a table student with attributes student name, roll number, total marks and percentage. Do the following operations Insert details in to the table Update
What do you mean by Correlated subquery? Subqueries, or nested queries, are used to bring back a set of rows to be used by the parent query. Depending on how the subquery is writ
Illustrate the statement 'Projection operation distributes over the union operation'. Give an example. Ans: Π L (E 1 ∪ E 2 ) = (Π L (E 1 )) ∪ (Π L (E 2 )) This says th
Explain the Attribute inheritance Ans: Throughout the rendering of the objects in a view, attribute sets of objects higher in the view hierarchy are inherited via objects below
A database administrator''s responsibilities and data contents
Define the terms i) Entity set ii) Relationship set Entity set: The set of all entities of the similar type is termed as an entity set. Relationship set: The set of all rela
Define entity integrity and referential integrity. How does SQL allow specification of these? Ans: Entity Integrity Rule- If the attribute A of relation R is a prime attribut
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