Book quantity under a Category in library management system - php

Question

I am building a library management system using PHP, Mysql. There is a category for each book. Users will be able to see how many books there are in each category. But I can't figure out how many books there are in each category. I want to find out how many books there are in each category.
<div class="row">
<div class="col-md-12">
<!-- Advanced Tables -->
<div class="panel panel-default">
<div class="panel-heading">
Categories Listing
</div>
<div class="panel-body">
<div class="table-responsive">
<table class="table table-striped table-bordered table-hover" id="dataTables-example">
<thead>
<tr>
<th>#</th>
<th>Category</th>
<th>Book Amount</th>
<th>Status</th>
<th>Creation Date</th>
<th>Updation Date</th>
<th>Action</th>
</tr>
</thead>
<tbody>
<?php
$sql = "SELECT tblcategory.CategoryName, tblcategory.Status, tblcategory.CreationDate, tblcategory.UpdationDate from tblcategory";
$query = $dbh -> prepare($sql);
$query->execute();
$results=$query->fetchAll(PDO::FETCH_OBJ);
$cnt=1;
if($query->rowCount() > 0)
{
foreach($results as $result)
{ ?>
<tr class="odd gradeX">
<td class="center"><?php echo htmlentities($cnt);?></td>
<td class="center"><?php echo htmlentities($result->CategoryName);?></td>
<td class="center">#</td>
<td class="center"><?php if($result->Status==1) {?>
Active
<?php } else {?>
Inactive
<?php } ?></td>
<td class="center"><?php echo htmlentities($result->CreationDate);?></td>
<td class="center"><?php echo htmlentities($result->UpdationDate);?></td>
<td class="center">
<a href="edit-category.php?catid=<?php echo htmlentities($result->id);?>"><button class="btn btn-primary"><i class="fa fa-edit "></i> Edit</button>
<a href="manage-categories.php?del=<?php echo htmlentities($result->id);?>" onclick="return confirm('Are you sure you want to delete?');"" > <button class="btn btn-danger"><i class="fa fa-pencil"></i> Delete</button>
</td>
</tr>
<?php $cnt=$cnt+1;}} ?>
</tbody>
</table>
</div>
</div>
</div>
<!--End Advanced Tables -->
</div>
</div>
My Database:
The Output Should be:

Answer 1

Calculate category wise book count by using subquery. Then use LEFT JOIN with main table. Use COALESCE() for replacing NULL value to 0.
SELECT c.CategoryName
, COALESCE(b.book_amount, 0) book_amount
, CASE WHEN c.Status = 1 THEN 'Active' ELSE 'Inactive' END Status
, c.CreationDate
, c.UpdationDate
FROM category c
LEFT JOIN (SELECT catid
, COUNT(id) book_amount
FROM book
GROUP BY catid) b
ON c.id = b.catid
ORDER BY b.book_amount DESC