3i Infotech Papers: Sample Questions 191 - 192 of 1245

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Question number: 191

» Database » MySQL

True-False▾

Question

Is the Following Statement True or False?

EXISTS, SOME, ANY are operators in SQL.

Answer

TRUE

Explanation

EXISTS operator:

  • Used to test for the existence of any record in a subquery.

  • Returns true if subquery returns one or more record.

Syntax:

SELECT column_name (s)

FROM table_name

WHERE EXISTS

(SELECT column_name FROM table_name WHERE condition);

SOME operator:

  • Compares a value to every other value in list or results from query.

  • It evaluates to true if the result of an inner query contains at least one row.

Syntax:

SELECT [column_name…. | expression1}

FROM [table_name]

Where expression2 comparison_operator {ALL|ANY|SOME} (subquery)

ANY operator:

  • ANY compares a value to every value in list or result from a query

  • It evaluates to true if the result of an inner query contains at least one row.

  • It is preceded by comparison operators.

  • Using greater ( > ) with ANY ensures result greater than at least one value.

Syntax:

SELECT [column_name…| expression1|

FROM [table_name]

WHERE expression2 comparison_operator {ALL|ANY|SOME} (subquery)

Question number: 192

» Operating System » Unix

Essay Question▾

Describe in Detail

What are the UNIX system calls for I/O?

Explanation

  • creat (name, permissions):

    • Used to creat a file with the name and mode specified.

    • Permission would a number.

  • open (name, mode)

    • Used to open a file name

  • close (fd)

    • Closes an opened file.

  • unlink (fd)

    • Deletes a file.

  • read (fd, buffer, n_to_read)

    • Reads data from a file.

  • write (fd, buffer, n_to_write)

    • Writes data to a file.

  • Iseek (fd, offset, whence)

    • Moves the read/write pointer to the specified location

  • Dup

    • Makes a duplicate copy of existing file descriptor.

  • Fcntl

    • Makes the changes to the properties of an open file.