What are the potential pitfalls of not properly aggregating non-aggregated fields in a GROUP BY clause in MySQL queries for PHP applications?

When not properly aggregating non-aggregated fields in a GROUP BY clause in MySQL queries for PHP applications, you may encounter errors or unexpected results due to the ambiguity of the non-aggregated fields. To solve this issue, make sure that all non-aggregated fields in the SELECT clause are also included in the GROUP BY clause. 

$query = "SELECT category, SUM(price) FROM products GROUP BY category";
$result = mysqli_query($connection, $query);

if($result){
    while($row = mysqli_fetch_assoc($result)){
        echo "Category: " . $row['category'] . ", Total Price: " . $row['SUM(price)'] . "<br>";
    }
} else {
    echo "Error executing query: " . mysqli_error($connection);
}

Keywords

MySQL GROUP BY non-aggregated fields PHP applications pitfalls

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