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Define the Query optimisation
The query parser commonly generates a standard initial tree to correspond to an SQL query, with no doing any optimization. Such type of a canonical query tree denotes a relational algebra expression that is extremely inefficient if executed directly. A query commonly has many possible execution strategies, and the process of choosing a appropriate one for processing a query is termed as query optimization. The major guidelines that are applied throughout query optimization are:
a. Combine a cascade of selections
b. Combine a cascade of projections
c. Commute selection and projection
d. Commuting selection with join / cartesian product Commuting projection with join or cartesian product
e. Commute projection with set operations
f. Commute selection with set operations
Explain the Project-Join normal form A relation R is in PJNF along with respect to a set of functional dependencies D if for all join dependencies of the outline *(R 1 , R 2 ,
What are the types of storage devices? Primary storage Secondary storage Tertiary storage Volatile storage Nonvolatile storage
The advantages of a database management system (DBMS) include :- Data integrity and elimination of duplication.
In an organisation various projects are undertaken. Each projects can employ one or more employees. Every employee can work on one or more projects. Each project is undertaken on
need to get answer for questions 3&4 on this page in part 1
What are the parts of SQL language? The SQL language has various parts: data - definitition language Data manipulation language View definition Transaction contr
Define tuple variable? Tuple variables are used for comparing two tuples in the same relation. The tuple variables are explained in the from clause by way of the as clause.
DISADVANTAGES OF RDBMS
What is Cardinality Ratio? Cardinality Ratios - The cardinality ratios for relationship kinds specifies the maximum number of relationship instances in which an entity can pa
Q. With the help of a suitable diagram gives module wise explanation of system architecture of DBMS. Sol. A Database management is a collection of interrelated data and col
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