Learn about query statements from a MySQL example

Since school so many years, have come to learn from an example is the fastest and most effective, and can cultivate a strong practical ability, which is a very
A good way to learn. Try not to visit. For example, when you look at a book, start with the examples from each chapter, and find out what you don't know and what you don't know or new knowledge.
And then targeted learning. Take a look at the following example:
<?php
$ip = getenv ("REMOTE_ADDR");
echo "$ip";
$conn =mysql_connect (' ip ', ' root ', ' * * * ');
mysql_select_db (' db ', $conn);
$sql = "Select *from counter where ip=" $ip ";";
$result =mysql_query ($sql, $conn);
$num =mysql_num_rows ($result);
$count =mysql_query ("Select*from counter", $conn);
$count =mysql_num_rows ($count);
echo "$num";
echo "$count";
if ($num ==0)
{
$sum = 1;
$count;
$sql = "INSERT INTO counter (ip,sum,countdata) VALUES (' $ip ', ' 1 ', ' $count ')";
mysql_query ($sql, $conn);
Mysql_close ($conn);
echo "$count";
}
Else
{
$my = "Select sum from counter where ip= ' $ip '";
$BBBBBB =mysql_query ($my) or Die (Mysql_error ());
$row =mysql_fetch_array ($BBBBBB);
@ $sum = $row [sum];
echo "$sum";
$sum;
$sql = "Update counter set sum= ' $sum ' where ip= ' $ip '";
mysql_query ($sql);
Mysql_close ($conn);
}
$str _count=strval ($count);
$str _count=chop ($str _count);
$count _len=strlen ($str _count);
$image _count= "";
if ($count _len<6)
{for ($j =0; $j <6-$count _len; $j)
{$image _count= $image _count. " ;
}
}
for ($i =0; $i < $count _len; $i)
{
$nom =substr ($str _count, $i, 1);
$image _count = $image _count. " $image _count = $image _count. $nom;
$image _count = $image _count. ". GIF ' > ';
}
echo "$image _count<br>";
Print "This is your first". $sum. " Visits ";