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Define the five basic operators of relational algebra?
Five basic operators of relational algebra are:1. Union (∪∪∪∪) - Selects tuples which are in either P or Q or in both of them. The duplicate tuples are eliminated.R = P ∪ Q2. Minus (-) - Removes generally common tuples from the first relation.R = P - Q3. Cartesian Product or Cross Product (××××) - The cartesian product of two relations is the concatenation of tuples belonging to the two relations and consisting of all probable combination of the tuples.R = P × Q 4. Projection (ππππ) - The projection of a relation is described as a projection of all its tuples over a few set of attributes, i.e., it yields a vertical subset of the relation. It is used to either decrease the number of attributes (degree) in the resultant relation or to reorder attributes. The projection of a relation T on the attribute A is denoted through πA(T).5. Selection (σσσσ) - Selects only some of the tuples, those satisfy given criteria, from the relation. It yields a horizontal subset of a given relation, i.e., the action is defined over a complete set of attribute names but just a subset of the tuples are involved in the result.R = σB(P)
Why are cursors necessary in embedded SQL? A cursor is an object used to store the output of a query for row-by-row processing through the application programs. SQL statements
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Need For Distributed Database Systems A distributed database is a set of database kept on multiple computers that appears to applications as a one database. As a result, an app
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Differentiate OO development from structured development. Structured approach of problem solving is based upon the idea of decomposition of system into subsystem. In this appro
Relational Algebra is a set of basic operations used to influence the data in relational model. These operations allow the user to specify basic retrieval request. The result of re
For every n-ary relationship type R where n>2, we make a new table S to represent R. We contain as foreign key attributes in s the primary keys of the relations that show the parti
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Q. Define a weak entity set and its identifying relationship. List the necessary conditions for a meaningful identifying relationship set of a weak entity set. Entity is a t
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