How does the SUM() function in PHP interact with the GROUP BY clause in a MySQL query?

When using the SUM() function in PHP with the GROUP BY clause in a MySQL query, you need to ensure that the columns you are grouping by are also included in the SELECT statement along with the SUM() function. This is because the GROUP BY clause groups the rows based on the specified columns, and the SUM() function calculates the sum for each group. Without including the grouped columns in the SELECT statement, MySQL will throw an error. 

<?php
// Connect to MySQL database
$mysqli = new mysqli("localhost", "username", "password", "database");

// Query to get the sum of a column grouped by another column
$query = "SELECT column1, SUM(column2) FROM table_name GROUP BY column1";

// Execute the query
$result = $mysqli->query($query);

// Fetch and display the results
while ($row = $result->fetch_assoc()) {
    echo "Column 1: " . $row['column1'] . ", Sum of Column 2: " . $row['SUM(column2)'] . "<br>";
}

// Close the connection
$mysqli->close();
?>

Keywords

PHP SUM() function GROUP BY clause MySQL query interaction

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