Database [3i Infotech Placement]: Sample Questions 9 - 10 of 294

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Question 9

Database
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Statement

True-False▾

All data files related to a Table space are removed when the Table space is dropped

Answer

FALSE

Explanation

Structure of Two Tablespace
  • A table space is a logical group of data files in a database.
  • Indicate the database storage location, not the logical database structure or schema
  • Using table space admin can control the disk layout of an installation.
  • DB contains at least one table space and usually two or more.
  • Database program automatically create a table space- SYSTEM.
  • A table space is made one or more data files.

Basically 4 Types of Table Spaces

  • Permanent:
    • Uses data files and normally contains the system and user data.
  • Temporary:
    • Temporary files are created temporary table space.
  • Undo:
    • It is permanent types of table space that are used to store undo data.
  • Read only:
    • It is a permanent table space it can only read, no write can take place, but table space can made read or write.
4 Types of Table Spaces

Question 10

Database
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Write in Short

Short Answer▾

Why can a “group by” or “order by” clause be expensive to process?

Explanation

  • GROUP BY, ORDER BY is executed by the Oracle engine. At the end, this leads to overhead, because whole data has to be rearranged again.
  • Group by: Combines all the similar rows and displays only the distinct data. Combining and displaying distinct data is an overhead.
  • Order by: Sorts the data either in ascending order or in descending order. Sorting the data is an overhead.
  • Processing of “group by” or “order by” clause requires creation of Temporary tables to process the results of the query, depending on the size of the result set can prove to be expensive.

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