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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
]};
What is the need for triggers? Triggers are useful mechanisms for alerting humans or for starting particular tasks automatically when particular conditions are met.
An entity set that does not have sufficient attributes to form a primary key is called? An entity set that doesn't have sufficient attribute to form a primary key is known as w
A Relation Schema represented by R(A1, A2, ..., An) is made up of the relation name the list of attributes and R Ai that it contains. A relation is described as a set of tuples
Explain the function of input controls. Identify four types of input control and explain the function of each. Provide an example of a data integrity error that could occur i
What are the basic objects of the data dictionary? Tables Domains Data elements Structures Foreign Keys
What is an object ID? Each class-derived table has an ID for primary key, one or more object IDs form primary key for association derived tables. An object ID is equivalent dat
Wait-die" scheme : The idea is based on non-preventive method. It is based on a simple rule: If Ti requests a database resource that is held by T
What is Index? An index is a physical structure having pointers to the data. Indices are created in an existing table to locate rows more quickly and efficiently. It is possibl
What is Identity? Identity (or AutoNumber) is a column that automatically produces numeric values. A start and increment value can be set, but most DBA leave these at 1. A GUID
waht is a repeating group?
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