Page 224 - DCAP402_DCAO204_DATABASE MANAGEMENT SYSTEM_MANAGING DATABASE

Unit 12: Query Processing and Optimization

12.11 Keywords Notes

Index scan: Search algorithms that use an index are restricted because the selection condition
must be on the search-key of the index.

Indexing: A database index is a data structure that improves the speed of operations on a database
table.
Join: Join operation is considered as the real power behind the relational database
implementations
Query cost: Cost is generally measured as total elapsed time for answering the query.

12.12 Self Assessment

Choose the appropriate answer:

1. RDBMS stands for:
(a) Relative Database Management System
(b) Relational Database Management System

(c) Relative Document Management System
(d) Relational Document Management System
2. CPU stands for
(a) Central Processing Unit (b) Control Processing Unit
(c) Central Power Unit (d) Central Power Utilization

Fill in the blanks:
3. Cost is generally measured as total elapsed time for answering the ...............................
4. The I/O cost depends on the ..................................

5. .................................. is applicable when the selection is an equality comparison on the
attribute on which file is ordered.
6. ............................... search retrieves a single record that satisfies the corresponding equality
condition.
7. Index scans can replace file scans if the join is an ...............................
8. The .............................. is applicable to equi-joins and natural joins only.

9. A join with a .............................. can be calculated either by using the nested loop or block
nested loop join
10. .................................. use equivalence rules to systematically generate expressions equivalent
to the given expression.

12.13 Review Questions

1. Describe various differences between DBMS and RDBMS.
2. What do you mean by query processing? Explain

3. How will you measure query cost? Explain.

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