Set - 6

Question 1 :

What is the difference between GROUP BY and ORDER BY in SQL?

Answer :

To sort a result, use an ORDER BY clause. 
The most general way to satisfy a GROUP BY clause is to scan the whole table and create a new temporary table where all rows from each group are consecutive, and then use this temporary table to discover groups and apply aggregate functions (if any).
ORDER BY [col1],[col2],...[coln]; Tells DBMS according to what columns it should sort the result. If two rows will have the same value in col1 it will try to sort them according to col2 and so on.
GROUP BY [col1],[col2],...[coln]; Tells DBMS to group (aggregate) results with same value of column col1. You can use COUNT(col1), SUM(col1), AVG(col1) with it, if you want to count all items in group, sum all values or view average.


Question 2 :

What is meant by MIME?

Answer :

Answer 1:
MIME is Multipurpose Internet Mail Extensions is an Internet standard for the format of e-mail. However browsers also uses MIME standard to transmit files. MIME has a header which is added to a beginning of the data. When browser sees such header it shows the data as it would be a file (for example image)
Some examples of MIME types:
audio/x-ms-wmp
image/png
application/x-shockwave-flash

Answer 2:
Multipurpose Internet Mail Extensions.
WWW's ability to recognize and handle files of different types is largely dependent on the use of the MIME (Multipurpose Internet Mail Extensions) standard. The standard provides for a system of registration of file types with information about the applications needed to process them. This information is incorporated into Web server and browser software, and enables the automatic recognition and display of registered file types.


Question 3 :

How can we know that a session is started or not?

Answer :

A session starts by session_start() function.
This session_start() is always declared in header portion. it always declares first. then we write session_register().


Question 4 :

What are the differences between  mysql_fetch_array(),  mysql_fetch_object(),  mysql_fetch_row()? 

Answer :

Answer 1:
mysql_fetch_array() -> Fetch a result row as a combination of associative array and regular array.
mysql_fetch_object() -> Fetch a result row as an object.
mysql_fetch_row() -> Fetch a result set as a regular array().

Answer 2:
The difference between mysql_fetch_row() and mysql_fetch_array() is that the first returns the results in a numeric array ($row[0], $row[1], etc.), while the latter returns a the results an array containing both numeric and associative keys ($row['name'], $row['email'], etc.). mysql_fetch_object() returns an object ($row->name, $row->email, etc.).


Question 5 :

If we login more than one browser windows at the same time with same user and after that we close one window, then is the session is exist to other windows or not? And if yes then why? If no then why?

Answer :

Session depends on browser. If browser is closed then session is lost. The session data will be deleted after session time out. If connection is lost and you recreate connection, then session will continue in the browser.


Question 6 :

What are the MySQL database files stored in system ?

Answer :

Data is stored in name.myd
Table structure is stored in name.frm
Index is stored in name.myi


Question 7 :

What is the difference between PHP4 and PHP5?

Answer :

PHP4 cannot support oops concepts and Zend engine 1 is used.
PHP5 supports oops concepts and Zend engine 2 is used.
Error supporting is increased in PHP5.
XML and SQLLite will is increased in PHP5.


Question 8 :

Can we use include(abc.PHP) two times in a PHP page makeit.PHP"? 

Answer :

Yes we can include that many times we want, but here are some things to make sure of:
(including abc.PHP, the file names are case-sensitive)
there shouldn't be any duplicate function names, means there should not be functions or classes or variables with the same name in abc.PHP and makeit.php


Question 9 :

What are the differences between mysql_fetch_array(), mysql_fetch_object(), mysql_fetch_row()?

Answer :

mysql_fetch_array - Fetch a result row as an associative array and a numeric array.

mysql_fetch_object - Returns an object with properties that correspond to the fetched row and moves the internal data pointer ahead. Returns an object with properties that correspond to the fetched row, or FALSE if there are no more rows

mysql_fetch_row() - Fetches one row of data from the result associated with the specified result identifier. The row is returned as an array. Each result column is stored in an array offset, starting at offset 0.


Question 10 :

What is meant by nl2br()?

Answer :

Anwser1:
nl2br() inserts a HTML tag <br> before all new line characters \n in a string.

echo nl2br("god bless \n you");

output:
god bless<br>
you


Question 11 :

How can we encrypt and decrypt a data presented in a table using MySQL?

Answer :

You can use functions: AES_ENCRYPT() and AES_DECRYPT() like:

AES_ENCRYPT(str, key_str)
AES_DECRYPT(crypt_str, key_str)

 


Question 12 :

How can I retrieve values from one database server and store them in other database server using PHP?

Answer :

For this purpose, you can first read the data from one server into session variables. Then connect to other server and simply insert the data into the database.


Question 13 :

Who is the father of PHP and what is the current version of PHP and MYSQL?

Answer :

Rasmus Lerdorf.
PHP 5.1. Beta
MySQL 5.0


Question 14 :

In how many ways we can retrieve data in the result set of MYSQL using PHP? 

Answer :

mysql_fetch_array - Fetch a result row as an associative array, a numeric array, or both
mysql_fetch_assoc - Fetch a result row as an associative array
mysql_fetch_object - Fetch a result row as an object
mysql_fetch_row —- Get a result row as an enumerated array


Question 15 :

What are the functions for IMAP?

Answer :

imap_body - Read the message body
imap_check - Check current mailbox
imap_delete - Mark a message for deletion from current mailbox
imap_mail - Send an email message