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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
]};
Define Partial Key and Primary Key A partial key, also known as discriminator, is the set of attributes which can uniquely identify weak entities that are related to similar o
State the data flow diagram of functional model Any action initiated by transition in the state diagram can be extended into an entire data flow diagram in functional model. Th
Discuss the problem of Spurious tuples and how we may prevent it. Ans: A spurious tuple is, mainly, a record in a database that gets created while two tables are joined bad
Forward Recovery (Redo): In this system the committed changes made by a transaction are reapplied to a previous copy of the database. In simpler
difference between MIS and DSS
Support by Adding Indexes Multiple indexes can be used to access a data file by multiple access paths. In such a scheme only single copy of the data is consider, only the numbe
Package classes and associations into models Programs are made of separate physical units which could be edited, imported, complied or otherwise manipulated. The careful part
What is an entity relationship model? The entity relationship model is a set of basic objects known as entities and relationship between those objects. An entity is a thing or
E-R model uses this symbol to represent weak entity set ? A Doubly outlined rectangle symbol is used to represent weak entity set.
Derived horizontal fragmentation: Some applications may include a join of two or more relations. If the relations are stored at dissimilar locations, there may be a major overhead
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