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Question number: 478

» Database » MySQL

Short Answer Question▾

Write in Short

What is an Entity?


Entities with example and its type

Entities with Example and Its Type

Entities with example and its type

  • Entity set is a entities of the same type that share the same properties.

  • For example, a STUDENT entity may have a Name, Roll number, Class, Marks etc. where STUDENT is the entity and name roll number class marks are the attributes.

Question number: 479

» Database » MySQL

Essay Question▾

Describe in Detail

What is the difference between TRUNCATE and DELETE commands?


Differentiate between the Truncate and Delete commands

Differentiate between the Truncate and Delete commands



DDL command

DML command.

No use of where clause

Where clause is used with DELETE to filter & delete specific records

Removes all rows from a table.

Used to remove rows from a table based on WHERE condition.

Minimal logging in transaction log- faster.

Maintains the log- slower than TRUNCATE.

Truncating a table requires ALTER permission.

To delete we need DELETE permission.

Uses less transaction space than Delete statement.

Uses more transaction space than Truncate statement.

Question number: 480

» Basic CS » Operating System

Essay Question▾

Describe in Detail

Define latency, transfer and seek time with respect to disk I/O.



  • Time required for a sub-system or its component to process a single storage transaction or data request.

  • Refers to length of time for- single data request to be received and right data found and accessed from the storage media.

  • For example, in a disk drive, latency is the controller to find the proper data blocks and place the head over those blocks to begin the transfer process.

Transfer time:

  • Time taken to actually transfer the data.

Seek time:

  • The time required to move the disk arm to the required track.

  • Seek time consist of two components:

    • The initial startup time.

    • In a disk drive it is the time taken by access arm to move the track.

      • The traverse time is not linear function of the number of tracks.

    • Average seek time: < 10 milliseconds