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MYSQL Tutorial

MySQL: Rows holding group wise maximum

Rows holding group-wise maximum

In this page, we have shown how to retrieve the rows holding group-wise maximum for a column.

In the example shown and explained in this page, we retrieved the most expensive books of each language.

Example:

Sample table: book_mast


Code:

SELECT book_name, pub_lang, book_price
FROM book_mast b1
WHERE book_price = 
SELECT MAX( b2.book_price )
FROM book_mast b2
WHERE b1.pub_lang = b2.pub_lang ); 

Explanation

The above MySQL statement has performed the following -

1. book_name, pub_lang, book_price are retrieved from book_mast, if

a) language of the most costly book of book_mast aliased as b2 and b1 are alike.

Sample Output:

mysql> SELECT book_name, pub_lang, book_price  
    -> FROM book_mast b1  
    -> WHERE book_price = (  
    -> SELECT MAX( b2.book_price )  
    -> FROM book_mast b2  
    -> WHERE b1.pub_lang = b2.pub_lang );
+----------------------------------+----------+------------+
| book_name                        | pub_lang | book_price |
+----------------------------------+----------+------------+
| Guide to Networking              | Hindi    |     200.00 | 
| Transfer  of Heat and Mass       | English  |     250.00 | 
| Fundamentals of Heat             | German   |     112.00 | 
| The Experimental Analysis of Cat | French   |      95.00 | 
+----------------------------------+----------+------------+
4 rows in set (0.00 sec)

PHP script

<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>example-rows-holding-group-wise-maximum-for-a-column php mysql examples | w3resource</title>
<meta name="description" content="PHP MySQL PDO Example">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
</head>
<body>
<div class="container">
<div class="row">
<div class="col-md-12">
<h2>List of most expensive books of each language : </h2>
<table class='table table-bordered'>
<tr>
<th>Book</th><th>Language</th><th>Price</th>
</tr>
<?php
$hostname="your_hostname";
$username="your_username";
$password="your_password";
$db = "your_dbname";
$dbh = new PDO("mysql:host=$hostname;dbname=$db", $username, $password);
foreach($dbh->query('SELECT book_name, pub_lang, book_price
FROM book_mast b1
WHERE book_price = (
SELECT MAX( b2.book_price )
FROM book_mast b2
WHERE b1.pub_lang = b2.pub_lang )') as $row) {
echo "<tr>"; 
echo "<td>" . $row['book_name'] . "</td>";
echo "<td>" . $row['pub_lang'] . "</td>";
echo "<td>" . $row['book_price'] . "</td>"; 
echo "</tr>";
}
?>
</tbody></table>
</div>
</div>
</div>
</body>
</html>

View the example in browser

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