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Define Query Processing
Query processing is the process of selecting the best plan or strategy to be employed in responding to a database request. The plan is then executed to produce a response. The component of the DBMS accountable for generating this strategy is known as a query processor. It is a step by step process. The first or initial step is to transform the query into a standard from. For instance, a query in QBE looked into by the research community. Query might be transformed into a relational algebraic expression; the optimization is carried out by substituting equivalent expressions for those in the query. In the next step a number of strategies known as access pans are generated for evaluating the transformed query. The physical characteristics of the data and any supporting access method are taken into account in producing alternate access pans. The cost of each access plan is calculated and the optimal one is selected and executed.
What are the DBMS languages? Briefly explain? Data Definition language (DDL):A database schema is specified through a set of definitions expressed through a special language
Determine the advantage of object-orientation Finally, object-orientation has advantage of continuity throughout analysis, persistent representation and design implementation.
define normalisation and functional dependency
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
To eliminate duplicate rows (distinct operator) Example: SELECT DISTINCT DEPTNO FROM EMP;
The Database administrator (DBA) uses the data dictionary in each phase of a database life cycle, beginning from the data gathering phase to the design, execution and maintenance p
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
Natural Join : It is the similar like Equi join except one of the duplicate columns is removed in the result table. The natural join is the most usually used form of join operation
what do you mean by consistency in rdbms?
All edges of a cube are expanding at a rate of 6 centimeters per second. How fast is the surface area changing when each edge is (a) 2 centimeters and (b) 10 centimeters?
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