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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
There are two major types of fragmentation: Horizontal& Vertical. Horizontal fragments, as the name suggests are subsets of tuples and vertical fragments are subsets of attributes
what is attribute is attribute inheritance in dbms?
Competition entrants can be either Individuals, or Teams. A Team is usually sponsored by a business, and, in that case, the team members would all wear T-shirts with the sponsoring
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create an er diagram for production management in film industry
domain
What is the main difference between read-only and update methods? A read-only method does not affect the values of a variable in an object, whereas an update method may alter t
What is system log? What are the entries? Ans: The system log that is generally written on stable storage contains the redundant data required to recover from volatile
Describe the statement in SQL which allows to change the definition of a table? In SQL Alter statement is used to allow the changes the definition of a table.
What is an ERD?
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