Pagination. Select from x number of tables - php

Question

i'm trying to make my second website using php and i'm stuck at some typical problem (i believe),
but very hard for me.
I'm making a page that show list of items depends on GET.
#1 if only "type" sended - show all items with x type.
#2 if only "tag" sended - show all items with x tag.
#3 if "type" and "tag" sended at the same time - show all items with x type and x tag.
problem #1 i solved this way
// items per page
$per_page = 5;
// 1) if isset type
if ( (isset($_GET['type'])) && (!isset($_GET['tag'])) ){
$type_id = get_safe_var($_GET['type']);
$con = mysql_connect(DB_HOST,DB_LOGIN,DB_PASSWORD) or die(mysql_error());
if ($con) {
mysql_select_db(DB_NAME) or die(mysql_error());
$sql = mysql_query("SELECT `item_type`, `item_type_name` FROM `item_types` WHERE `type_id` = '$type_id'");
$row = mysql_fetch_assoc($sql);
$type = $row['item_type'];
$type_name = $row['item_type_name'];
if ($type != ''){
$pages_query = mysql_query("SELECT COUNT(`id`) FROM `".$type."` WHERE `insearch` = '1'");
$number_of_pages = ceil( mysql_result($pages_query, 0) / $per_page );
$current_page = ( (isset($_GET['page'])) && ((int)$_GET['page'] > 0) ) ? (int)$_GET['page'] : 1;
$start = ($current_page - 1) * $per_page;
echo "<h1>$type_name</h1>";
$sql = mysql_query("SELECT `id`, `name`, `img` FROM `".$type."` WHERE `insearch` = '1' ORDER BY `id` DESC LIMIT $start, $per_page");
// echo items
while ($row = mysql_fetch_assoc($sql)){
$id = $row['id'];
$name = $row['name'];
$img = $row['img'];
echo "
<div id='items_cell'>
<img alt='$name' src='$img' width='145' height='200' /><br />
<a href='open_item.php?type=$type_id&id=$id'>$name</a><br />
<em>$type_name</em>
</div>";
}
}
mysql_close($con);
} else {echo 'sql connection error';}
}
pagination
// echo pagination
// 1) if isset type
if ( (isset($_GET['type'])) && (!isset($_GET['tag'])) ){
if ( (isset($number_of_pages)) && ($number_of_pages >= 1) && ($current_page <= $number_of_pages) ){
for ($i = 1; $i <= $number_of_pages; $i++){
if ($i == $current_page){
echo "<li><a href='?type=$type_id&page=$i' class='sel'>$i</a></li>";
} else {
echo "<li><a href='?type=$type_id&page=$i'>$i</a></li>";
}
}
}
}
I'm stuck at problem #2.
I got tag ID. Need to show all items with that tag.
I don't understand how to make a SELECT from x-number of tables with a working paginatin.
database structure -
Any help is welcome!
P.S. Maybe i need to change db structure to make SELECT easier?

Answer 1

You should definitely work on your table design. Having dynamic table names is a big NO-NO as you won't ever be able to do any useful joins. Just create one big tag-table and add a column type like you did in your table item_types.
To solve problems #1-#3 just build the WHERE-part of your query dynamically:
// empty selection
$where = array();
if (!empty($_GET["type"])
$where[] = "`item_type` = '".mysql_real_escape_string($_GET["type"])."'";
if (!empty($_GET["tag"])
$where[] = "`tag` = '".mysql_real_escape_string($_GET["tag"])."'";
$query = "SELECT ... FROM `item`"
// Join type-table
. " JOIN `item_types` ON `item`.`id` = `item_types`.`item_id`"
// Join all of this item's tags
. " JOIN `item_tags` ON `item`.`id` = `item_tags`.`item_id`"
// Filter tags by item_type
. " AND `item_types`.`item_type` = `item_tags`.`item_type`"
;
if (count($where) > 0)
$query .= "WHERE ".implode(" AND ", $where);