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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 cartesian product in Database Management System
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Critically evaluate the bulleted list of information-related items in this case study. How are each contradictory to the notion of being an information-literate knowledge worker?
For every multivalued attribute 'A', we make a new relation R that contains an attribute corresponding to plus the primary key attribute k of the relation that shows the entity typ
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Depending upon the rules we have found, we can classify the locks into two types. Shared Lock: A transaction might be acquiring shared lock on a data item in order to read it
does tables are called relations
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