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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
]};
Set Difference If R1 and R2 are two union compatible relations or relations then result of R3 =R1- R2 is the relation that have only those tuples that are in R1 but not in R2.
What is a foreign key, and what is it used for? A foreign key is used to establish relationships between relations in the relational model. Technically, a foreign key is a colu
What is DML Query Langauge? Data Manipulation Language (DML) - A data manipulation language is a language in which enables users to access or manipulate data as organized throu
Before defines the second type of integrity constraint, viz., Entity Integrity, we should be well-known with the concept of NULL. Mostly, NULL is intended as a basis for dealing
List the types of authorization. A) Read authorization B) Write authorization C) Update authorization D) Drop authorization
examples of fields in a database
What is key ? Key - A single attribute or a combination of two or more attributes of an entity set which is used to recognize one or more instances (rows) of the set (table) is
In how many parts events are classified Events are classified as four types in UML 1. Signals 2. Calls 3. Passing of Time 4. Change in State
Compare the two log-based recovery schemes in terms of ease of implementation and overhead cost. Ans: There are two types of log based recovery techniques: deferred update
2NF Normal Form : A relation schema process R is in 2NF if it is in 1NF and each non-prime attribute A in R is fully functionally related on primary key. Second normal form (2N
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