RDBMS Questions and Answers – Query Processing – Selection Operation & Sorting

This set of RDBMS Multiple Choice Questions & Answers focuses on “Query Processing – Selection Operation & Sorting”.

1. Which of the following are steps in query processing?
a) Parsing and translation
b) Optimization
c) Evaluation
d) All of the mentioned

Explanation: Parsing and translation, optimization, evaluation are all the basic steps to process a query.

2. A relational algebra operation annotated with instructions on how to evaluate it is called _______
a) Evaluation algebra
b) Evaluation plan
c) Evaluation primitive
d) Evaluation engine

Explanation: A relational algebra operation annotated with instructions on how to evaluate it is called Evaluation primitive. The evaluation primitive is the basis for evaluation of queries.

3. A sequence of primitive operations that can be used to evaluate a query are called as __________
a) Query evaluation algebra
b) Query evaluation plan
c) Query evaluation primitive
d) Query evaluation engine

Explanation: A sequence of primitive operations that can be used to evaluate a query are called as Query evaluation plan. This is used by the query evaluation engine to process the queries.

4. The lowest level operator to access data in query processing is _______
a) File scan
b) File manipulation
c) File handling
d) File organization

Explanation: The lowest level operator to access data in query processing is file scan. File scans are algorithms that locate and retrieve records that fulfill a selection criterion.

5. Search algorithms that use an index are referred to as _________
a) Index scans
b) Search scans
c) Primary scans
d) Equality scans

Explanation: Search algorithms that use an index are called as index scans. We use the selection predicate to guide us through the choice of index to use in processing the query.

6. Sorting of relations that do not fit in memory is called as _______
a) Internal sorting
b) External sorting
c) Overflow sorting

Explanation: Sorting of relations that do not fit in memory is called as external sorting.

7. A selection of the form satisfying the intersection of all records satisfying individual simple conditions is
a) Conjunctive selection
b) Disjunctive selection
c) Negation
d) None of the mentioned

Explanation: A selection of the form satisfying the intersection of all records satisfying individual simple conditions is a conjunctive selection. This is a form of complex selection predicate.

8. A selection of the form satisfying the union of all records satisfying individual simple conditions is
a) Conjunctive selection
b) Disjunctive selection
c) Negation
d) None of the mentioned

Explanation: A selection of the form satisfying the intersection of all records satisfying individual simple conditions is a disjunctive selection. This is a form of complex selection predicate.

9. A selection of the form giving all the records not satisfying simple individual conditions is ______
a) Conjunctive selection
b) Disjunctive selection
c) Negation
d) None of the mentioned

Explanation: A selection of the form giving all the records not satisfying simple individual conditions is negation. This is a form of complex selection predicate.

10. Which of the following can be implemented?
a) Conjunctive selection using one index
b) Conjunctive selection using composite index
c) Conjunctive selection by intersection of identifiers
d) All of the mentioned

Explanation: Conjunctive selection using one index, conjunctive selection using composite index and conjunctive selection by intersection of identifiers can be implemented. These are A7, A8, A9 algorithms that use an index.

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