When should DISTINCT be used in PHP queries and when should it be avoided?

DISTINCT should be used in PHP queries when you want to retrieve unique rows from a result set, eliminating duplicates. It should be avoided when you are sure that the result set will not contain duplicate rows or when the performance impact of using DISTINCT is significant.

// Using DISTINCT in a PHP query
$query = "SELECT DISTINCT column_name FROM table_name";
$result = mysqli_query($connection, $query);

// Fetch and display the results
while ($row = mysqli_fetch_assoc($result)) {
    echo $row['column_name'] . "<br>";
}