Database-MySQL [3i Infotech Placement]: Sample Questions 88 - 90 of 162

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Question 88

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Write in Short

Short Answer▾

What operator tests column for the absence of data?

Explanation

  • IS NULL operator tests column for the absence of data.
  • Comparing a column to NULL using the = operator is undefined.
  • Instead, use WHERE IS NULL or WHERE IS NOT NULL.

Syntax of IS NULL:

SELECT “column name”

FROM “table_name”

WHERE “column_name” IS NULL

Question 89

Question

MCQ▾

Select ‘NORTH’ CUSTOMER From CUST_DTLS Where REGION = ‘N’ Order By CUSTOMER Union Select ‘EAST’ CUSTOMER From CUST_DTLS Where REGION = ‘E’ Order By CUSTOMER The above is

Choices

Choice (4)

a.

Error-the string should be in double quotes

b.

Not an error

c.

Error-ORDER BY clause

d.

Error-the string in single quotes ‘NORTH’ and ‘SOUTH’

Answer

c.

Explanation

Error in the ORDER BY clause. Since ORDER BY clause cannot be used in UNIONS.

Question 90

Edit

Describe in Detail

Essay▾

What is DBMS?

Explanation

  • A DBMS is a software that allows creation, definition and manipulation of database
  • . Dbms is actually a tool used to perform any kind of operation on data in database.
  • Any piece of information can be a data, for example name of your school.
  • Database is actually a place where related piece of information is stored and various operations can be performed on it.

Components of Database System

Understanding of Components of Database System
  • Users:
    • Users may be of various type such as DB administrator, System developer and End users.
  • Database application:
    • Database application may be Personal, Departmental, Enterprise and Internal
  • DBMS:
    • Software that allow users to define, create and manages database access, Ex: MySql, Oracle etc.
  • Database:
    • Collection of logical data.

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