Short note on Query Processing .

-

Query Processing 

  • Query Processing is a translation of high-level queries into low-level expressions. It is a step-wise process that can be used at the physical level of the file system, query optimization, and actual execution of the query to get the result.
  • It requires the basic concepts of relational algebra and file structure. It refers to the range of activities that are involved in extracting data from the database. It includes the translation of queries in high-level database languages into expressions that can be implemented at the physical level of the file system.
  • Query Processing is the process of converting high-level queries to low-level expressions to extract the data from physical level file systems like databases.  OR,
  • Query Processing would mean the entire process or activity which involves query translation into low-level instructions, query optimization to save resources, cost estimation or evaluation of query, and extraction of data from the database

It involves mainly four steps

  • Parsing and translation
  • Optimization
  • Evaluation
  • Execution





Comments

Post a Comment

Popular posts from this blog

Suppose that a data warehouse for Big-University consists of the following four dimensions: student, course, semester, and instructor, and two measures count and avg_grade. When at the lowest conceptual level (e.g., for a given student, course, semester, and instructor combination), the avg_grade measure stores the actual course grade of the student. At higher conceptual levels, avg_grade stores the average grade for the given combination. a) Draw a snowflake schema diagram for the data warehouse. b) Starting with the base cuboid [student, course, semester, instructor], what specific OLAP operations (e.g., roll-up from semester to year) should one perform in order to list the average grade of CS courses for each BigUniversity student. c) If each dimension has five levels (including all), such as “student < major < status < university < all”, how many cuboids will this cube contain (including the base and apex cuboids)?

-
Image
a) A Snowflake Shema is shown in figure below: b) The specific OLAP operations to be performed: 1. Roll-up on course from course_id to department. 2. Roll-up on a student from student_id to university. 3. Dice on course, student with department ="CS" and university = "biguniversity" 4. Drill-down on a student from the university to student_name. c) N = 4 dimensions The cube will contain 54 = 625 cuboids.
Read more

Discuss classification or taxonomy of virtualization at different levels.

-
Image
Taxonomy of virtualization Virtualization is mainly used to emulate the execution environment, storage, and networks. The execution environment is classified into two: – Process-level – implemented on top of an existing operating system.  – System-level – implemented directly on hardware and does not or minimum requirement of the existing operating system. OR,  Virtualization covers a wide range of emulation techniques that are applied to different areas of computing. A classification of these techniques helps us better understand their characteristics and use  V irtualization is mainly used to emulate  ● Execution Environments: To provide support for the execution of the programs eg. OS, and Application.  ○ Process Level: Implemented on top of an existing OS that has full control of the hardware  ○ System Level: Implemented directly on Hardware and do not require support from existing OS.  ● Storage: Storage vi...
Read more

Short note on E-Government Architecture

-
Image
1)  Presentation layer The presentation layer identifies and describes the system users, who require access to government information at different capacities, and the channels through which information can be accessed.  During system development, one is required to explicitly identify the government user, the system is intended to serve, and also the means through which this information is to be accessed so that the system can be tailored to meet these requirements. It manages the user’s interface with the system. If a pro- project is to be successful, different stakeholders need to be identified at the beginning, involved in the initial stages and kept involved throughout development and implementation. 2) E-government layer E-government public services utilize very specialized applications that are only available to certain agencies and not all agencies participating in the consortium. The main goal of the e-government layer is to achieve a government that;  does not as...
Read more