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What is meant by heuristic optimisation? Discuss the main heuristics that are applied during query optimisation.
Ans: In heuristic optimization, heuristics are employed to reduce the cost of optimization in place of analyzing the number of different plans to make out the optimal plan. For instance, a heuristic optimizer would make use of the rule 'Perform selection operation as early as possible' without finding out whether the cost is reduced by this transformation. Heuristics approach generally assists to reduce the cost but not all the time. The major heuristics that are applied throughout query optimization are:
Define weak and strong entity sets? Weak entity set: entity set that do not have key attribute of their own are known as weak entity sets. Strong entity set: Entity set that
Surgeons identified by doctor ID (DOCID) operate on patients identified by patient ID (PATID) in operating theaters identified by room numbers (ROOMNO). Each surgeon can operate on
The Locking Protocol: To manage concurrency related problems we use locking. A lock is mainly a variable that is associated with a data item in the database. A lock can be located
The ABC Bank authority now wants to create a database for their customers. So you are requested to modify your program of Assignment A3 as follows. The main program first displa
Type of views : Simple views and Difficult Views Feature Simple Views Complex Views Number of tables One
What is known as fudge factor? The number of partitions is enhanced by a small value called the fudge factor, which is usually 20 percent of the number of hash partitions compu
Do you have experts of the dbms
Explain the EXISTS and UNIQUE functions of SQL. Give an example for each? EXISTS: The EXISTS function takes one parameter that is a SQL statement. If any records exist which
Briefly describe concurrency execution? Lock - based protocols Locks There are several modes in which a data item may be locked in this section we restrict our attention
The entity type STUDENT has the following attributes: Student Name, Address, Phone, Age, Activity, and No of Years. Activity represents some campus-based student activity, and No o
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