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MySQL STDDEV() function

STDDEV() function

MySQL STDDEV() function returns the population standard deviation of expression.

The STDDEV() function is used to calculate statistical information for a specified numeric field in a query. It returns NULL if no matching rows found.

Syntax:

STDDEV(expr);

Where expr is an expression.

MySQL Version: 5.6

Example: MySQL STDDEV() function

The following MySQL statement returns the standard deviation of 'total_cost' from purchase table.

Sample table: purchase


Code:

SELECT STDDEV(total_cost)             
FROM purchase;

Sample Output:

mysql> SELECT STDDEV(total_cost)             
    -> FROM purchase;
+--------------------+
| STDDEV(total_cost) |
+--------------------+
|         315.392172 | 
+--------------------+
1 row 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-STDDEV()- php mysql examples | w3resource</title>
<meta name="description" content="example-STDDEV()- php mysql examples | w3resource">
<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>Standard deviation of total purchase:</h2>
<table class='table table-bordered'>
<tr>
<th>Standard deviation of total purchase</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 STDDEV(total_cost) 
FROM purchase') as $row) {
echo "<tr>";
echo "<td>" . $row['STDDEV(total_cost)'] . "</td>";
echo "</tr>";
}
?>
</tbody></table>
</div>
</div>
</div>
</body>
</html>

View the example in browser

JSP script

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@ page import="java.sql.*" %>
<%@ page import="java.io.*" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>example-stddev()</title>
</head>
<body>
<%
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
String Host = "jdbc:mysql://localhost:3306/w3resour_bookinfo";
Connection connection = null;
Statement statement = null;
ResultSet rs = null;
connection = DriverManager.getConnection(Host, "root", "datasoft123");
statement = connection.createStatement();
String Data = "SELECT STDDEV(total_cost) FROM purchase";
rs = statement.executeQuery(Data);
%>
<TABLE border="1">
<tr width="10" bgcolor="#9979">
<td>Standard deviation of total purchase</td>
</tr>
<%
while (rs.next()) {
%>
<TR>
<TD><%=rs.getString("STDDEV(total_cost)")%></TD>
</TR>
<%   }    %>
</table>
<%
rs.close();
statement.close();
connection.close();
} catch (Exception ex) {
out.println("Can’t connect to database.");
}
%>
</body>
</html>

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