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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
]};
UNION If R1 and R2 are two union compatible relations then R3 = R1 ∪ R2 is the relation having tuples that are either in R1 or in R2 or in both. In case, R3 will have tuples
what is er digram given that example of hospital,bank and library er digram.
External failure : A failure can also result because of an external cause, such as earthquakes, fire, floods, etc. The database must be duly backed up to avoid troubles occurring d
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
Given the following relations Vehicle (Reg_no, make, colour) Person(eno, name, address) Owner(eno, reg_no) Write expressions in the relational algebra to answer the following
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4. Describe three ways to handle missing field values
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
Describe Data Manipulation language ? Data Manipulation Language (DML) - A data manipulation language is a language which enables users to access or manipulate data as organize
sy bcs project of hospital managment system
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