select

how to know how many rows in that table
select count(columnheader) from database2.studentinfo;
examples
$query = 'SELECT `first` , `last` FROM `a_database` ORDER BY `id` ';	ist select the two columns with  headeer names, to display in ascending order
$query = 'SELECT `first` , `last` FROM `a_database` WHERE `id`<5  ORDER BY `id` ';	select two columns with header names , to display it hase to pass condtion, which has id is less than 5, that’s display, in an ascending order its display ascending order of id
$query = "SELECT `name` FROM `foods` WHERE `type` = '$fv' ";	type is column header name, select name column header and to display  it matched with fv, which one has matched that rows onl display , from customer
$query = "SELECT `hits` FROM `hits_count` WHERE `id` = 1 ";	select hits column to display it hase to pass condtion, its display only 1 id row
$query = "SELECT `ip` FROM `hits_ipaddress`";	display ip column
$query = "SELECT `ip` FROM `hits_ipaddress`";	display ip column from database
$query = "SELECT `ip` FROM `hits_ipaddress`";
$query = "SELECT `hits` FROM `hits_count` WHERE `id` = 1 ";	select hits column header to display it passs condtion means It display only one row
$query = "SELECT `name` FROM `foods` WHERE `name` LIKE '%$s_text%' ";
$query = "SELECT `id` FROM `users` WHERE `username` = '$username' AND `password` = '$pass_hash' ";
$query = "SELECT `$field` FROM `users` WHERE `id` = '$id' ";
$query =" SELECT `username` FROM `users` WHERE `username` = '$username'";
SELECT `id` FROM `users` WHERE `username` = '' or ''='' AND `password` = '' or ''=''
$query = "SELECT `email` FROM `users` WHERE `id` =$id";
$query = "SELECT `email` FROM `users` WHERE `id` =$id";