Difference between Primary Key and Unique key in mysql?

Difference between Primary Key and Unique key in mysql/sql/oracle?

SNO	Primary Key	Unique Key
1	Primary Key does not allow NULLs values in a table	Unique Key allows Nulls value in a table
2	Only one primary key will be there in a table	More than one unique key will be there in a table
3	Clustered index is created in primary key in a table	Non-Clustered index is created in unique key in a table
4	Primary key allows each row in a table to be uniquely identified and ensures that no duplicate rows exist as well as does not allow the duplicates values in the rows of a table.	Unique key constraint is used to prevent the duplication of key values within the rows of a table and allow null values

By default Primary Key creates a Clustered Index on the column as same as Unique Key creates a Nonclustered Index. Another major difference is Primary Key doesn’t allow NULLs, but Unique Key allows NULLs. We can create only one primary key in a table, but a table can have the multiple unique key.

Update query in mysql

The syntax for Update the row into tables,

UPDATE
    table_name SET (colname1, colname2, colname3 ...) VALUES (value1,value2,value3,...) WHERE colname = row_values;   

<?php

$con = mysql_connect('localhost', 'root','');
mysql_select_db('dbname', $con) or die(mysql_error());

$query = "UPDATE table_name SET rank="2" WHERE sno = 2";   
$ok = mysql_query($query);

if($ok)
echo "Updated row successfully";
else
echo "Failed to update the row in the table";

?>

sno	name	marks	rank	post_of_date
2	krishnan	397	2	09-04-2001
3	PHP Developer	521	36	27-03-2012

Delete query in mysql with php

The syntax for Delete the row into tables,

DELETE FROM
    table_name WHERE colname = row_values;    

<?php

$con = mysql_connect('localhost', 'root','');
mysql_select_db('dbname', $con) or die(mysql_error());

$query = "DELETE FROM table_name WHERE sno = 1";    
$ok = mysql_query($query);

if($ok)
echo "Deleted row successfully";
else
echo "Failed to delete the row in the table";

?>

sno	name	marks	rank	post_of_date
2	krishnan	397	3	09-04-2001
3	PHP Developer	521	36	27-03-2012

Insert query in mysql with php

The syntax for inserting values into tables,

INSERT INTO
    table_name (`col1`, `col2`, `col3`,.....)
    VALUES ('val1', 'val2', 'val3',.....);    

<?php

$con = mysql_connect('localhost', 'root','');
mysql_select_db('dbname', $con) or die(mysql_error());

$query = "INSERT INTO table_name (`sno`, `name`, `marks`, `rank`,`post_of_date`) VALUES ('3', 'PHP Developer', '521', '36',now())";    
$ok = mysql_query($query);

if($ok)
echo "Inserted successfully";
else
echo "Data's are not inserted in to table";

?>

sno	name	marks	rank	post_of_date
1	Ram	407	3	09-04-2001
2	krishnan	397	3	09-04-2001
3	PHP Developer	521	36	27-03-2012

Show the content or text when mouse over the link

<style type="text/css">
<!--
.box {
background-color: #F4F4F4;
border: 1px solid #CCC;
height: 150px;
width: 225px;
padding: 5px;
display:none;
position:absolute;
}


-->
</style>
<script type="text/javascript" language="JavaScript">
var cX = 0; var cY = 0; var rX = 0; var rY = 0;
function UpdateCursorPosition(e){ cX = e.pageX; cY = e.pageY;}
function UpdateCursorPositionDocAll(e){ cX = event.clientX; cY = event.clientY;}
if(document.all) { document.onmousemove = UpdateCursorPositionDocAll; }
else { document.onmousemove = UpdateCursorPosition; }
function AssignPosition(d) {
if(self.pageYOffset) {
rX = self.pageXOffset;
rY = self.pageYOffset;
}
else if(document.documentElement && document.documentElement.scrollTop) {
rX = document.documentElement.scrollLeft;
rY = document.documentElement.scrollTop;
}
else if(document.body) {
rX = document.body.scrollLeft;
rY = document.body.scrollTop;
}

How to delete checked checkbox rows in php?

<?php
if($_REQUEST['btndelete'] != '')
{
    if(!empty($_REQUEST['checkboxstatus'])) {
        $checked_values = $_REQUEST['checkboxstatus'];
        foreach($checked_values as $val) {
            $sqldel = "delete from subscribe where id = '$val'";
            $resdel = mysql_query($sqldel);
            if($resdel)
                $error_log = 1;
            else
                $error_log = 2;
        }
    }
}

How to send the email in php?

Easily send the email in php, you have to follow some steps
<?php
    $mail_to = "phprockers.blogspot@gmail.com";
    $mail_subject = "Introducing New concept in PHP";
    $body_content = "Hi <br/> We are introducing new method in php as well as we are teaching php clearly. Please click here and watch <a href='http://phprockers.blogspot.in/'>php tutorial</a>";
    if(mail($mail_to, $mail_subject, $body_content)){
        echo "Email sent successfully";
    } else {
        echo "Email sending problem. Please try again.";
    }
?>

How to send the email with attachment in php?

Very simple to send the email with attachment with php validation.

First we have to write html form for upload the attchement.

<form name="uploadRes" enctype="multipart/form-data" method="post" action="<?php echo $_SERVER['PHP_SELF'];" >
<input type="file" name="resume" id="resume" />
<input type="submit" name="res-submit" id="res-submit" value="Send Resume"  />
</form>

Validation for attaching the file. Here we have to find the file type, then send the email to particular function.

if($_REQUEST['res-submit'] != '') {
    if(!empty($_FILES)) {
        function getExt($file) {
            $dot = strrpos($file, '.') + 1;
            return substr($file, $dot);
        }