3i Infotech Papers: Sample Questions 221 - 222 of 1245

Examrace Placement Series prepares you for the toughest placement exams to top companies.

Question number: 221

» Database » MySQL

Essay Question▾

Describe in Detail

What is “transparent DBMS”

Explanation

  • It is one, which keeps its Physical Structure hidden from user.

  • A query with respect to DBMS relates to user commands that are used to interact with a database.

  • The query language can be classified into data definition language and data manipulation language.

  • Transparent hides implementation details from the user.

  • For example in a centralized DBMS, data independence is a form of transparency it hides changes in the definition and organization of the data from the user.

  • A DDBMS may provide a various· levels of transparency.

  • They all participate in the same overall objective: to make the use of the distributed database, equivalent to that of a centralized database.

Four types of transparency in DDBMS:

  • Distribution transparency

  • Transaction transparency

  • Performance transparency;

  • DBMS transparency.

Question number: 222

» Database » Oracle

MCQ▾

Question

Which of the following is not correct about Cursor?

Choices

Choice (4) Response

a.

Cursor holds temporary results

b.

SQL uses implicit Cursors to retrieve rows

c.

Cursor is a named Private SQL area

d.

Cursor is used for retrieving multiple rows

Answer

a.

Explanation

Define cursor and its types

Define Cursor and Its Types

Define cursor and its types

Cursor:

  • Used for retrieving set of rows.

  • Essentially formed by assigning a name to a SELECT statement and manipulate the information within SQL statement.

  • Contains information on a select statement and rows of data accessed by it.

  • Holds more than one row, but it can process only one row at a time.

  • Multiple rows that the cursor holds form the active set.

Two types of cursors:

  • Implicit Cursors

  • Explicit Cursor

Two types of cursors

Two Types of Cursors

Two types of cursors

Implicit Cursors:

  • Automatically generated by oracle when an SQL statement is executed.

  • Created to process the statement when DML statements like INSERT, UPDATE, and DELETE etc. are executed.

Provide some attribute:

  • % FOUND

    • Return value is TRUE if DML statements like INSERT, DELET and Update at least one or more rows and return one or more rows.

  • %NOTFOUND

    • Return value is TRUE if DML statement like INSERT, DELETE and UPDATE affect no row, or a SELECT INTO statement returns no row.

    • It is a opposite of % FOUND.

  • %ISOPEN

    • Returns FALSE for implicit cursor, because the SQL cursor automatically closes after execution.

  • %ROWCOUNT

    • Returns the number of rows affected by DML statement like INSERT, UPDATE, DELETE.

Provide some attribute

Provide Some Attribute

Provide some attribute

Explicit cursors

  • Defined by programmers to gain more control on the context area.

  • Declaration section of the PL/SQL block.

  • Created on a SELECT statement which returns more than one row.

Syntax:

CURSOR cursor_name IS select_statement; ;

Steps of Creating Explicit cursor:

Declare the cursor:

  • Define name of cursor with a name and associated with SELECT statement

    Syntax:

    CURSOR name IS

    SELECT statement;

  • Open the cursor:

  • Allocate memory for the cursor to fetch the rows returned by the SQL statement.

    Syntax:

    OPEN cursor_name;

  • Fetch the cursor:

  • Access one row at a time. We can fetch row from the above-opened cursor.

    Syntax:

    FETCH cursor_name INTO variable_list;

  • Close the cursor:

  • Release the allocated memory

Syntax

Close cursor_name;