Database [3i Infotech Placement]: Sample Questions 74 - 75 of 294

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Question 74

Database
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Describe in Detail

Essay▾

What are the wildcards used for pattern matching?

Explanation

Undrstanding of Wildcards
  • Wildcard character is used to substitute other character in a string.
  • Used with SQL LIKE operator.
  • LIKE operator is used in a WHERE clause to search a specified pattern in a column.

Two wildcards used in LIKE operator:

  • %- Represent zero, one, or multiple characters.
  • _ - Represent a single character.

Syntax of %

SELECT FROM table_name

WHERE column LIKE ‘XXXX %’ or ‘% XXXX %’

Syntax of _

SELECT FROM table_name

WHERE column LIKE ‘XXXX_’ or ‘_XXXX’ or ‘_XXXX_’

Question 75

Database

Question

MCQ▾

LGWR process writes information into … .

Choices

Choice (4)

a.

Redo log files

b.

Database

c.

Control files

d.

None of the above

Answer

a.

Explanation

Structure Understanding of LGWR
  • LGWR process writes information into redo log files.
  • Redo log files are created upon database creation and addition one time added by the DBA.
  • When we start a database instance, LGWR is an oracle background process created.
  • Writes the redo log buffers to the on-line redo log files.
  • Redo log data is always written first to a buffer in memory, and then written to disk by the LGWR process.

The LGWR process is also responsible for:

  • When a transaction is committed, writing commit records to the log file
  • Multiple commits that is written in a single operation when database activity is high.
  • Recording a system change number to each committed transaction, for use in recovery operations when running Parallel Server.

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